Alan J. Borsuk, Sarah Carr and Leonard Sykes Jr. of the Milwaukee Journal Sentinel investigate 15 years of vouchers in Milwaukee in a seven-part series. They found that "...56% of the students enrolled at Catholic elementary schools in the city of Milwaukee participate in choice." They also discovered that it's tougher to assess the quality of a voucher school than an open one.
Looks like you haven't made a choice yet.