Nationally, EVAAS has become the biggest player in the market, partly because it is the oldest and best-known VAM around--when the Obama administration created the Race to the Top initiative (which pushed states to adopt value-added models to hold teachers accountable for student learning), EVAAS was well-positioned to beat out other software products.
Further, EVAAS's marketing claims are powerful and attractive.
Keep in mind that the state- and district-level officials who went ahead and purchased EVAAS had little capacity to judge whether such promises were realistic or wildly overblown.
It should be no surprise, then, that EVAAS has been unable to live up to its own hype.
See, for example, Figure 1, which shows that while EVAAS was in use for educational reform purposes in Houston (i.e.
Given the student achievement data, it seems clear that the use of EVAAS did not result in the gains that Houston's superintendent anticipated; there is no evidence of that.
EVAAS is still the most popular proprietary VAM in use throughout the U.S.
In our own recent analysis, we looked specifically at Houston's experience with EVAAS: We analyzed more than 1,700 Houston teachers' value-added results, from 2012 to 2015, to investigate the software maker's core claim about the quality of its product, the argument that it delivers "precise, reliable, and unbiased results that go far beyond what other simplistic [value-added] models found in the market today can provide."
And we are concerned about model transparency, since we have heard anecdotally and seen reported in recent research (e.g., Collins, 2014; Kappler Hewitt, 2015) that EVAAS is less accessible and more enigmatic than other VAMs in the market.
Unlike the EVAAS model described previously, the work evaluating TPPs in North Carolina and Louisiana, and New York City which used VAM with direct estimation incorporated a wide array of controls at the student, classroom, and school levels (Boyd et al., 2009; Henry et al., 2011; Henry, Thompson, Fortner, et al., 2010; Noell, 2006).
In the most common VAM using aggregation, EVAAS, the full complement of available test scores for each student are used to isolate teachers' effects.