This report presents findings from the first detailed study of Baltimore's 5 year high school reform. Using administrative data, Urban Institute researchers found that test scores and attendance rates were higher for students in Baltimore's innovation high schools than in the city's comprehensive or newly formed neighborhood high schools. Students in innovation and neighborhood schools also showed more stability in their enrollment than their counterparts in comprehensive schools. These findings remained after controlling for students' backgrounds and previous achievements even though students at innovation schools were more academically advantaged than their peers in other schools prior to entering high school.