Mathematica's study of The Equity Project examined the charter school’s instructional and personnel strategies, student characteristics and attrition rates, and impacts on student achievement during the school’s first four years.
By the end of the 2012–2013 school year, impacts on student achievement were consistently positive across subjects and cohorts, with especially large effects in math.
Here's an excerpt from the Wall Street Journal article, "Charter School Boasts Big Pay and Big Results," by Leslie Brody.
"A small New York City charter school opened five years ago with an attention-grabbing premise: Paying teachers $125,000 salaries would lure ace faculty and help poor children learn.
A new study of the middle school, called The Equity Project, suggests that the experiment is working. The report to be released Friday by Mathematica Policy Research said the school’s students made more progress than similar children attending traditional city schools.
After four years at the charter school, eighth-graders showed average test score gains in math equal to an additional year and a half of school, compared with district students. The study found these charter students’ gains equaled more than an extra half-year in science and almost an extra half-year in English."