The Globe today highlights an MIT/Harvard study of Boston-area charter and 'pilot' schools, in which charter schools steadily outperformed both the pilot schools -- essentially, charter-style schools run by the city with union contracts for teachers and staff -- and Boston's traditional public schools. The study documents striking gains in middle-school math -- gains that are reflected here in New York's 78 public charters, despite profound gaps in early-grade math scores.

Citywide, only about half of third-graders in charter schools score at level 3 or 4 on state math exams (54%), compared with 87% of third-graders in the city's hundreds of non-charter elementary schools. By eighth grade, though, the balance has flipped: Three-fourths of charter students score level 3 or 4 in math, compared with 60% citywide.

Some might attribute the gains to the focus many charters place on drills, skills, and testing, while others contend that without basic skills, kids can't progress to master more sophisticated content. No one can argue that stronger parent engagement, a characteristic many charter schools share, drives attendance and thus achievement: Kids who show up learn more. Notably in Boston, charter schools are characterized as "independent public schools dedicated to innovative teaching," while New York's charters extend the DOE's familiar focus on achievement and accountability.

The pesky 'details' nearly always overlooked deserve loud mention: According to the New York City Charter Center annual report, charters serve far, far fewer English Language Learners than other city schools -- only about 3% of charter students need language instruction, compared with 14% of students citywide. (Yes, that's nearly five times as many.) And students who require special education count for only 9% of charter students overall, compared with 14% of public-school students. The Center says charters are "marginally behind" other public schools in this regard, but from here, the gap doesn't seem marginal at all: Non-charter public schools have a third more special-needs students, many of whom require a level and sophistication of services charters cannot provide, such as special, self-contained classes and cash-intensive resources, like adaptive gyms, speech instruction, and physical and occupational therapy.

So all well and good to compare apples with apples -- but when the fruit bowl's more inclusive, it's important to recognize what goes into the mix.