Do many kids make it through in only four years at your school? Our kids made it through in four at a big U, but it took some summers to do it. One changed disciplines within the same college at the U after 1 1/2 years or so, which required taking a few classes to replace some that were already taken. And all had the problem of not enough sections of certain required classes being available or filling up immediately. The school was encouraging students to graduate in four, and then not providing some of the classes to do so!
If it's the same at your school, is your 2015 really 2016, or ... Now you wouldn't be thinking of abandoning some of those stragglers, would you?