But different value - added models make different assumptions about how much variation in test scores should be attributed to teachers. (carnegieknowledgenetwork.org)
It compares the effects of Head Start with a measure of variation in test scores (the test score standard deviation) across students at the end of Head Start or the beginning of kindergarten. (investinginkids.net)
Consistent with other research on school effects, we find that the school a student attends can explain a substantial share of the overall variation in test scores: that single factor explains 34 percent of the variation in math scores and 24 percent of the variation for reading. (educationnext.org)