Andrew has inspired me to hop on his coattails concerning the way we look at NECAPs (so read his post first). Basically, I've been putting off posting how we can look at the same NECAP data in two ways. As Andrew explains, the "value-added" method would be to follow the cohorts (ie; the same group of kids from year to year). Andrews task of digging deeper into how we can tease out data comparing 8th grade and 11th grade scores for essentially the same group of kids is more difficult than what I am going to look at: comparing cohorts from year-to-year in elementary schools.
Here is a made-up example of how we're usually asked to "read" the NECAP scores. (Let's assume these are writing scores for "Quahog Elementary School"). Generally, we are given data that is "shaped" so that we look at the change from year to year for each grade like this:
GRADE | 2005 | 2006 | GROWTH | 2007 | GROWTH | 2008 | GROWTH | 2009 | GROWTH |
3 | 63% | 76% | 13% | 76% | 0% | 76% | 0% | 78% | 2% |
4 | 73% | 65% | 8% | 77% | 12% | 75% | 2% | 73% | 2% |
5 | 63% | 89% | 22% | 75% | 14% | 78% | 3% | 85% | 10% |
6 | 72% | 68% | 4% | 78% | 10% | 75% | 3% | 85% | 10% |
AVERAGE | 69% | 75% | 6% | 77% | 2% | 76% | 1% | 80% | 4% |
Year in Grade 3 | 2005 | 2006 | GROWTH | 2007 | GROWTH | 2008 | GROWTH | 2009 | GROWTH |
2005 | 63% | 65% | 2% | 75% | 10% | 75% | 0% | - | - |
2006 | - | 76% | - | 77% | 1% | 78% | 1% | 85% | 6% |
2007 | - | - | - | 76% | - | 76% | 0% | 85% | 10% |
I believe that looking at the data by comparing different cohorts at the same grade level provides some value in assessing progress, however, I believe that a better method--one that is probably more fair to teachers and the students within a given cohort-- is the alternative method outlined above.