How Much Should We Grow?

How Much Should We Grow?As NWEA prepares to release 2015 norms this summer, I am exploring the thoughtful use of norms in a series of four posts. The first post focused on understanding what norms are and how to judge the quality and usefulness of normative data. The second post explained what status norms are, how to interpret them, and how they may be used to make decisions about students. The third post explored how NWEA leverages our norms data to link to instructional content. In this final post, I will focus on growth norms both for the individual and for the school.

Why Understanding Growth is Important

An understanding of growth as captured in growth norms provides an important context for evaluating programs and for evaluating claims about the efficacy of potential new programs. Many curricular providers offer case studies that follow a pre-test/post-test model and then determine if the change between the two scores is statistically significant. Some have even used MAP data in this way. Focusing on the change from pre- to post- test can be misleading, as growth may occur with or without the curriculum product, so it can be difficult to assign attribution for the growth. The real questions educators want answered are:

  • Did students show more or less growth than expected?
  • Did students do better than they would have had we not implemented this program?
  • For what percent of the students was this instruction successful?

NWEA growth norms provide the tools that MAP partners need to answer these questions. Partners can see how much each student grew and where that growth is in terms of a percentile for each student. Aggregating that data provides the most useful information for judging a program’s effectiveness. I acknowledge that there are many other factors in judging efficacy of a program or in evaluating potential new programs, but simply note my focus here is norms. But looking at a program’s usefulness through the lens of either student or school growth norms makes the most sense. In looking at evidence for new program adoption, educators should discount evidence that simply compares pre and post test scores to claim success.

Student Growth Norms

The real power of MAP and MPG is in measuring growth over time and in being able to compare each student’s measured growth to growth norms. The real power of MAP and MPG is in measuring growth over time and in being able to compare each student’s measured growth to growth norms. NWEA makes this easy for educators by offering the Conditional Growth Index (CGI) which allows for comparisons based on subject, grade-level, starting RIT and instructional weeks. Using growth norms, teachers can not only determine whether a student met or missed a target, but also where that student’s growth stands in comparison to other students with similar starting RIT scores and weeks of instruction—percentile rank. Accounting for instructional progress in growth norms is something only NWEA offers. Growth norms provide teachers the necessary context for setting individual student growth targets, a powerful way to help students take ownership of their own learning. With the 2015 norms release, NWEA will provide a table showing mean growth for each grade through grade 8 for three time periods: fall > winter, winter > spring and fall > spring. Each mean will be accompanied by the standard deviation. The standard deviation gives a good indication of how clustered the range of student growth is around the mean score.

School Growth Norms

NWEA is providing school level norms for 2015 in a manner that is much easier to use. In the new reports educators will no longer need to use the Achievement Status and Growth (ASG) calculator in the ASG Summary Report, and school norms will be built into the Student Growth Summary Report. Though the reports will eliminate having to rely on the calculator, it will still be available. School level norms are useful to compare the performance of one grade to the performance of the same grade as in the national norms. The school level norms provide a conditional growth index (CGI) which accounts for instructional weeks for each grade and a percentile for the CGI to make the comparison straightforward. School norms are a particularly useful – and really a fairer – way to compare groups and to compare the performance of a group over time because group performance is much harder to change than individual performance. The 2015 growth norms cover six periods, up from four in 2011. NWEA will provide a table showing school mean growth for each grade through grade 8 for three of those time periods: : fall > winter, winter > spring and fall > spring. Each mean will be accompanied by the standard deviation. The standard deviation for a grade level is much smaller showing that grade level scores are more clustered around the mean than individual scores, emphasizing the point that group scores are harder to change.

Better and Easier

NWEA understands the importance of our norms data. With each release of the norms, we try to offer the highest technical quality data we can by incrementally improving our psychometric processes. In the 2015 release we have also made strides in making the data easier to access and use.