The Chicago Public Schools touts studies on its Web site meant to support a 7.5 hour school day, which CPS will implement next year. However, authors of two of the studies took issue with CPS using their work to support its longer school day policy.

Erika Patall of the University of Texas told the Sun-Times that "a good deal of research does not rule out something other than time causing the improvement" for better student performance. Also, a National Center on Education Statistics researcher contends CPS misleadingly extrapolated information from a chart they did on optimal weekly instructional minutes.

Yesterday, a coalition of 16 parent groups demanded to meet with Mayor Rahm Emanuel and go over the research the mayor and CPS have used to support the 7.5 hour day.