The data recorded concerning student time-on-task behavior suggests that involvement in an authentic problem keeps students more engaged. This is an important finding because students learn more (assuming the task is appropriate and challenging) when their time-on-task behavior is higher (Bloom, 1974). Students in the PBL experimental classroom had 4.27 more minutes per 45-minute class session of time-on-task behavior than their comparison group. This would result in an additional 21.35 minutes of engaged science instruction per week, and an overall gain of 12.80 hours of science over the course of the school year.