My problem is that there are only two weeks left at school (and in fact they seem to be winding down already). Our paediatrician thinks we should wait until fall to try, once he's back in school, but I'm not so sure.
My son always found those last few weeks of school the most difficult to stay focused, because he was using the 'come on team, lets meet this challenge' spirit of school to help him focus, and so when everyone else got less focused, he really had a hard time.
So if the pead is willing, I would encourage him to start 'medications merry-go round' now.
From my perspective, most of what you are trying to do isn't to find one that works (they mostly all work if you do a high enough dose) but to find one that works without causing moodiness, or other side effect issues - and that's very variable one kid to another. So summertime is a fine time to at least get a general idea of which ones your child 'feels like himself' on. You will need to tweak along the way, possibly when school starts, or growth spurts, or major changes in physical activity level.
You can always pick up a summer activity that would help you see if the med is working, such as starting a musical instrument. My son's ability to practice without parental supervision changed dramatically with medication.
Best Wishes,
Grinity