Chang-Tai Hsieh and Miguel Urquiola are unable to find any signs that vouchers made a positive difference for education in Chile:
When Schools Compete, How Do They Compete? An Assessment of Chile's Nationwide School Voucher Program: In 1981, Chile introduced nationwide school choice by providing vouchers to any student wishing to attend private school. As a result, more than 1,000 private schools entered the market, and the private enrollment rate increased by 20 percentage points, with greater impacts in larger, more urban, and wealthier communities. We use this differential impact to measure the effects of unrestricted choice on educational outcomes. Using panel data for about 150 municipalities, we find no evidence that choice improved average educational outcomes as measured by test scores, repetition rates, and years of schooling. However, we find evidence that the voucher program led to increased sorting, as the best public school students left for the private sector.
This is very important. There are few even half-decent studies of the impact of voucher programs. We know that the Texas data that was thought to support the Bush initiatives was in fact fraudulent, so this Chilean data has even greater weight.
The only effect seems to be a segregation of students by abilities. The public schools get the less able students, and probably all the special needs students.
This is very much what US educators have claimed would happen.
I'm not surprised that the students academic performance was little changed. There's very little data that any curricular change makes a great difference in the outcome for the average student.