Dive Brief:

• Low-income students who won a lottery to attend private school via vouchers in the District of Columbia score lower on math tests, even after two years, according to a federal analysis from the Institute of Education Sciences. Washington has the only federally-funded voucher program in the country. 
• Proponents of school choice are downplaying the results, noting that other criteria should be weighed, such as graduation and college acceptance rates, as well as parent satisfaction. The fact that the math tests were voluntary, with only 75% of voucher winners and 66% of students not using vouchers taking it, has cast some doubt on the reliability of the results. 
• Some of the most recent research on voucher programs show that test scores drop at first and then sometimes — though not always — bounce back. The study's authors maintain that the evaluation could not assess the value of school choice in general but only the effect of adding a private school option to an environment that already had choices in education. (Many students in Washington, D.C., attend charter schools.)

Dive Insight:

The federal study authors echo many experts in that when trying to evaluate the impact of school choice programs, it's difficult, if not virtually impossible, to compare apples to apples. The thorn in the side of those who attempt it is the ways in which the student bodies come together at these private and charter schools. Part of the student population is self-selected, as the parents and children are choosing it on their own. Does that mean they're better researchers and/or more serious about education, and thus more likely to perform well? Or maybe the opposite is true — that it's students and parents who have all but given up on school and are looking for another option.

Some schools operate under laws that require open enrollment, while others can have their own admission criteria. And then there's the fact that private and charter schools have fewer students with disabilities than public schools. Lastly, any school's demographics are always affected by the demographics of its neighborhood. So what stymies researchers in making a case for or against school choice is that very little about the students to be studied is random.

An Urban Institute study found that, in cities where school choice was entrenched, black students traveled farther to school than their white or Hispanic school mates. With so many vagaries to try to account for in assessing the pros or cons of a school choice program, what is known for sure? That private schools and charter schools propel local public schools to up their game. When competition comes to town, the public schools tend to improve (though at least one study showed that effect tapers off). And that brings us, arguably, full circle: If all public schools were created equal in regards to funding and resources, we might not need school choice programs at all.