If a student has given up, if they are not willing to sit for March and May tests, they certainly have not taken advantage of every possible opportunity and would not likely be given permission to participate in the graduation.
It's a way to make sure that by the senior year you're not losing any (students) in the 11th hour. It's seeing the kids through to the end and meeting their needs all the way through.
Any student who participated in the May testing but for whom we do not yet have scores by the June ceremonies could participate in graduation activities. Essentially, we're giving those students the benefit of the doubt.