I went to an engineering school that had a very difficult time with their drop out rate. One of the biggest indicators of success, meaning graduation, was the

I went to an engineering school that had a very difficult time with their drop out rate. One of the biggest indicators of success, meaning graduation, was the students incoming math ability. Basically, if the student came in and took anything less than calculus when they first arrived, it was more likely than not that they'd drop out. Eventually, the math department added mandatory attendance to all lower level math courses and the affect was dramatic. The graduation rate went way up for these students. Now, graduation rate is only one possible metric. That said, many universities do have hard data and that data generally states that classroom attendance leads to better outcomes overall. Certainly, that doesn't work for all students, but it does suggest that there still is a tangible, substantial difference between being in class and not.