If Vyvanse was helping in the classroom, but poor appetite was a problem, there are things you can do to combat the appetite issue and continue with the medication that helps him best. Cyproheptadine/Periactin is commonly prescribed for this exact issue in kids with ADHD. It stimulates the appetite. My son didn’t gain weight for about 2 years — one year on Cyproheptadine and he was up 12-15 lbs. It was extremely helpful.
There are other strategies too:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism