Growth Model FAQ's
Overview of the
NGMA: Definition, purpose, background.
What is the Nevada Growth Model of Achievement?
The Nevada Growth Model of Achievement is the newest component of
the State's educational measurement system. It is a statistical model that
calculates each student's progress on state assessments. It is currently a tool
for displaying school and district results, and in the future has potential
for displaying student results. It is a high-quality, valid and reliable
measure of student academic growth which will be reported annually based on
The NGMA produces accurate growth scores, even at the
highest and lowest levels of academic achievement. As of 2011, schools with
4th-8th graders will receive growth scores for Mathematics and Reading. In
future, the NGMA will expand to include other areas, if
Why does Nevada need a growth measure?
Nevada needs a growth measure. For
the last decade, we have built an assessment and accountability system for
public education that has a single, primary goal: to set a proficiency bar
and hold students and schools accountable to meeting it. But we know that
setting a proficiency goal based solely on achievement status is not enough
to help all of our students grow and achieve the most they can. While
testing for proficiency is informative, knowing whether a child is
proficient or not cannot answer some of the most important questions we
have in classrooms across the state. These questions include: Is my
child growing in her academic learning? Are my child's teachers and his
school providing what he needs to grow well?
The most important
use of this measurement tool s to expand our vision of what is happening in
schools and to promote meaningful conversations across the state about what
it takes to move students along in their learning. The NGMA has potential
to support program design, professional learning, assessment, and
curriculum and instruction.
What is the purpose of the NGMA?
purpose of the NGMA is to enhance current school accountability measures so
we can better understand how to support student growth. The NGMA provides a
new way to track growth in student achievement-both growth of individual
students and growth of groups of students.
What can the NGMA tell us about student and school growth? What questions can the NGMA help answer?
results are analogous to the height or weight growth chart you might review
with a pediatrician. The doctor can use the chart to tell you how well
your child is growing in height or weight in relation to their peers. The
NGMA results tell you how well your student is growing in achievement in
relation to his or her peers. The School Growth Score (SGP) is the median
student growth score for a school.
The NGMA results can help answer
important questions such as:
- How much did
my student's school grow this year?
- How much would the school's student body need to grow in
achievement to reach the proficiency target?
- Is my student's school achieving in a way that will prepare
students for college and career-readiness?
- What effect has a school or teacher had on student
What is student growth?
Growth is change over time. USED defines
student growth as the change in student achievement for an individual
student between two or more points in time. In other words, student growth
is the rate of learning for a student. Groups of students can be
tracked, too, since growth can be aggregated by classroom, school,
subpopulation, or district.
What are the student growth scores and how do they compare "academic peers"?
The student growth percentile (SGP) is
the basic metric of the NGMA. The SGP is the percentage of students, starting
at the same place that a student's growth exceeded. The NGMA scores are
technically called "student growth percentiles (SGP) since they report student
growth in terms of how a student's achievement is compared to their "academic
peers" over time. Academic peers, in this case, are students who have the same
score histories on the CRT. This means that students are compared fairly to
other students across the state. Each student in Grades 4-8 receives a growth
score for Math and Reading, and the median (akin to the average) of these
scores for a given school produces the NGMA School Growth Score.
How is growth different than proficiency?
Growth tells us something different than
whether or not a student or school has "hit the bar" by passing the
assessment. In other words, growth tells a different story than proficiency
alone. Right now, Adequate Yearly Progress (AYP) reports whether schools
hits a target for proficiency. Growth will add a new dimension to our
understanding: now we can look at how a school is doing in moving students
toward proficiency-or beyond it. NGMA results can complement measures of
achievement status such as those used in AYP Reporting.
Why is the NGMA considered to be complementary to the current state system of assessments?
The NGMA is not currently part of the Adequate Yearly Progress
(AYP) analysis, but serves as a complement to AYP. The NGMA itself produces
information about each and every student's annual growth patterns, and it can
support various aggregations of student scores to help identify growth
patterns across groups. It is a high-quality, valid, and reliable measure of
student academic growth that can be compared across the state at each grade
level/subject area. As of early 2011, schools with 4th-8th graders will
receive growth scores for Mathematics and Reading, although the NGMA may be
expanded in the future to include other grade levels or subject areas or to
be reported by student, classroom, or subpopulation.
NGMA is not the only measure educators can use to judge growth. In a
balanced assessment system, many measures are used to judge how students are
progressing. For example, teachers evaluate student growth all the time.
Also, remember that the School Growth Score does not tell us whether a given
student is proficient against the Nevada Content Standards or how students
are growing in all subject areas. Furthermore, the measure cannot determine
important things, like school or teacher effectiveness, without other
supporting information. The NGMA provides meaningful information to
complement what we already know about student learning.
Where did the NGMA come from?
Assembly Bill 14 required the Nevada Department of Education
(NDE) to adopt a growth model to measure student achievement annually based on
the CRT results. The model design was required to track the progress of pupils
enrolled in a public school from year to year to "determine whether the
school has made progress in the achievement of pupils" (Nevada Revised
Statutes, 2009, 385.3595).
Section 1 Chapter 385 of NRS is hereby
amended by adding:
|1. The Department shall adopt a
model to measure the achievement of pupils enrolled in grades 3 to 8,
inclusive, based upon the results of the examinations administered pursuant
to NRS 389-550. The model must be designed so that the progress of pupils
enrolled in a public school may be tracked from year to year to determine
whether the school has made progress in the achievement of pupils.
|2. The board of trustees of each school district and the
governing body of each charter school shall apply the model in the format
required by the Department. The information collected must be used to
determine whether individual schools have made progress in the achievement
of pupils. (Nevada Revised Statutes, 2009, 385.3595).
The NDE decided to select a model that could also be used to
inform the State's reform agenda and improvement planning. Furthermore, the
NDE saw the growth model as a key reporting element within a balanced
assessment system. Assembly Bill 14 (NRS 385) provides for NDE to develop a
growth measure for statewide use.
Why didn't Nevada measure student growth previously?
Nevada needed three elements critical to
growth models to be in place:
- A Statewide
individual student tracking system (the System of Accountability
Information for Nevada (SAIN).
- Statewide assessments administered in consecutive grades in
the same subjects (Nevada Proficiency Examination Program assessments
- A technically sound and
understandable method for measuring growth that was compatible with the NPEP
Nevada now has three of
these elements to support NGMA.
What are the goals of the pilot NGMA for the 2010?
During this initial phase of the NGMA, efforts have focused on
developing, testing, and implementing the model and on disseminating
information about the NGMA and gathering feedback from users.
What are the next steps for the NGMA?
The first results of School Growth Scores will be
published by the NDE by early 2011. These results will be the first time
statewide growth data has been reported publicly.
Again, the purpose of
the NGMA is to provide a new way to track growth in student achievement-both
growth of individual students and growth of groups of students. The most
important purpose of this measurement tool is to expand our vision of what is
going on in schools and to promote more meaningful conversations across the
state's educational community about what it takes to move students along in
their learning. During the latter part of Phase 1: Preparing for Growth and
during Phase 2: Designing a Growth System, the NGMA Steering Committee will
guide the NDE as we develop the model to capture more information about
student growth in achievement.
When will public reports on the pilot NGMA be available?
For this initial pilot phase (Phase 1:
Preparing for the NGMA), the NDE will report only on statewide and district
growth relative to the statewide norm. The 2010 NDE NGMA report, to be
released in August of 2011, will be based on an aggregation of included
students of all state public schools and will report only statewide data.
Prior to the publication of the report, the NDE will continue the process of
gathering feedback information to validate the model and to plan improvements
and further implementation of the NGMA during Phase 2.
Related to the NGMA
How was the NGMA Developed?
2009-2010, the NDE designed and piloted the NGMA using statewide assessment
data from 2005-06 through 2008-09. The pilot project included evaluating
data quality, analyzing specifications, and evaluating the impact of
results. The results of the pilot formed the foundation for the
development of system requirements and organization within the State's
student information system (SAIN).
The NGMA was designed
collaboratively with districts. A work group representing nine districts
from across the state and NDE staff members drove the work and periodically
updated district Test Directors, Curriculum Directors, and NDE's Technical
Advisory Committee. In the fall of 2010, a steering Committee representing
districts, higher education, charter schools, the Nevada State Education
Association, the Legislative Counsel Bureau, and the NDE was formed to
further the work of the NGMA project and guide policy related to current and
future developments of the project.
The technical work was supported
by Damian Betebenner of National Center for the Improvement of Educational
Assessment. Dr. Betebenner worked with Colorado, Indiana, Massachusetts,
and other states on development of their state growth models. Further
support came from the Nevada Proficiency Examination Program (NPEP)
Technical Advisory Committee, a committee of experts in the field of
educational measurement and advisors to the development, administration, and
use of the CRT.
The NGMA work group first established criteria for
selecting a model. They decided that the model must be:
- valid and reliable metric that is communicable
and technically sound;
- provide new
information that is currently masked by the model used for AYP
- be supported by the
state's assessment data system;
compatible with test scales that are horizontally aligned; and
- allow for fair and useful interpretation of
Other growth models
were evaluated in the course of the NGMA pilot. Gains difference models,
residual gains models, and Value-Added Models (VAM) (e.g., Raudenbush,
2004; McCaffrey, D. Lockwood, J.R., Koretz, D.M., and Hamilton, L.S, 2004)
were evaluated against the selection criteria. Drawbacks of the other
candidate models included less flexibility for future uses, incompatibility
with Nevada's CRT program (i.e., requirement of vertical test scales),
controversy in other states and school districts across the country over the
validity of the models, and lack of flexibility to changes in assessment
Student Growth Percentiles (Betebenner, 2008) method was
therefore selected because it met all the State's requirements for a viable
model. The model compares each student's achievement to his or her academic
peers, in other words, students are compared with the other students who
had the identical past performance on the CRTs for the prior three
How does the NGMA work?
The underlying model uses the annual
Criterion-Referenced Test (CRT) scores from the past four years and produces a
percentile score. This score tells you how the student ranks among her peers
for her rate of growth: If she is in the 60th percentile, she is growing at a
rate of 10 percentiles higher than the typical student in the state. If she is
in the 40th percentile, she is growing at a rate 10 percentiles lower than the
typical student in the state. Since students are compared to students with the
same past achievement patterns, the NGMA produces accurate growth scores even
at the highest and lowest levels of academic achievement.
What can School Growth Scores tell us?
Student's individual scores are ranked in percentiles,
depending on how much they have grown from year to year. The median of theses
student scores produce a School Growth Score. The School Growth Scores can be
categorized to help interpret what it means. A score between the 40th and
60th percentiles is typical growth. Growth below the 40th percentile
is less than typical growth while growth above the 60th percentile is
more than typical.
What is the median growth percentile and how is it used under Phase 1 of the pilot NGMA?
The median growth
percentile is a summary of individual student growth rates by district,
school, or by any other grouping of interest. For the pilot NGMA reporting
as part of Phase 1, only the district and school aggregations will be
reported. During Phase 2, further uses of the median growth percentile are
How is the median score calculated?
The median is calculated by
taking the individual student growth percentiles of all the students in the
group being analyzed, ordering them from lowest to highest, and identifying
the middle score, which is the median. The Median is more appropriate to use
the averages when summarizing a collection of percentile
What steps did the NGMA work group take to test run the growth model?
the NGMA work group defined the population of students to be included in the
tryout as all Nevada students in grades 3-8 who took Mathematics and Reading
CRTs over four years.
Next, we ran the Student Growth Percentiles
(SGP) for Mathematics and Reading (Betebenner, 2008).
evaluated the results by comparing the results with those of the other
candidate methods, replicating the results at the NDE and district offices,
reviewing the results for reasonableness, and identifying a reasonable
definition of "typical" growth.
We found that the School Growth Score
could be fair and useful information to inform educational
Who was included in the NGMA pilot?
The NGMA pilot included over 330,000
student cases of CRT test takes from 2005-2006 through 2008-2009. The
demographic representation was typical of the Nevada student body year to
year (i.e., 1.5% American Indian, 8% Asian/Pacific Islander, 11.5% African
American, 36 Hispanic, 43% White, 11.5% Special Education, 18% English
Language Learners, 34% free or reduced-lunch status).
What were the results of the NGMA pilot?
The NGMA pilot resulted in reasonable results for
Nevada schools. Of the 508 schools evaluated, 462 schools fell in the
"typical" range for Reading between the 40th and 60th percentile. For Math,
454 fell in the 40th-60th percentile range. As we learn more about the best
ways to apply the data, we will be able to provide even more ways to
interpret the results.
Results of the NGMA pilot are summarized in graphic
form in the appendix. Schools are represented in scatterplots to report
their 2009 Pilot School Growth Scores versus their 2009 AYP proficiency
rates. The charts can be interpreted to show how some schools may be showing
high growth but may not meet the AYP targets. Likewise, some schools may
meet AYP targets but are not showing high growth. Still other schools are
showing either strength or weakness in both areas of