Every year we go to DW the week before President's Day because DH attends a conference being held near Disney. From at least 10 years of experience, I can tell you that the crowds will be very to moderately low the Mon-Thurs before Pres. Day. For the most part, there will be no lines or very short waits for all the major attractions. On Thursday afternoon things will begin to pick up and by Friday, the lines will average 20-60 minutes depending on the ride. From Saturday on, it is CROWDED!!
We have been in the parks when there were cheerleading groups, choral groups, and various other school groups attending events at Disney. We have never felt that they have an impact on the crowds during the first part of the week.