If it is available in the area, co-op is a fantastic way to go. He will spend a half day doing (paid) army stuff, and the other half of the day doing his english and math courses. He'll come out of the semester with BMQ and SQ under his belt, and will hit the ground running for DP1 over the summer.
Also, a (reserve) summer BMQ and SQ course typically take a month each (maybe 3.5-4.5 weeks depending on weekends off, etc). It's very common for a young soldier, like your son, to go away for July and August, and come home with both courses completed. The issue, is that his DP1 Infantry course (to qualify him in his trade) will take an additional month. He will be stuck waiting until the following summer to get loaded on that course.
If it is available, by taking a fall/winter part time BMQ course, he would then free himself to do SQ/DP1 in the summer, and come home a full qualified private.
If it's not available, he will have to wait out for the entire year to get his qualification (some units will let SQ qualified soldiers train with the unit, others won't, I cannot comment on his specific one).
It's just something to keep in the back of your head, to fast track his progress.
