Well, I’m no expert so I would consult with your doctor before making any decisions, but I do not give my 9 years old son meds during summer. I just stopped the day after the last day of school (he also takes Vyvanse 20mg). Since then I have given him the meds twice since school ended because we were going to an important event and I wanted him to be in his best behavior. For summer camp I do not give him the meds because after all there he can play, play and play so no need for sitting and paying attention to the teacher.
Every child is different therefore every child reacts different to the starting and stopping of the meds, for this reason consult his doctor. That is what I did and he gave me the green light and so far he is ok with not having his meds during the summer except when we are going out to something that requires his attention or tranquility.

My two boys are now 14 and 18, and they have never taken their med in the summer or on weekends. (until one started Strattera, but that’s a different class of meds)

Many college kids only take stimulants when they need them, instead of daily as we do with our kids. This allowed my boys to have some input in their medication (it wasn’t an option to NOT take it on school days) as well as an opportunity to increase their caloric intake and catch up on any missed growth. The only disadvantage I saw, was that Mondays were tough.  The boys were a bit sluggish and tired, but got back to normal by Tuesday.

As my oldest got to about 11th grade, he was able to decide on specific days that he did’t need his meds, based on what would be happening in school that day. That was also a sign of maturity to me.

My 12-year-old does not take meds during the summer. He primarily has the inattentive component of ADHD, so he doesn’t really need to be on his game in the focus department during summer vacation. Also, the stimulant tends to curb his appetite a bit, so it gives his body a chance to bulk up and gain a bit of weight since he’s on the small side. I agree with the first post…make sure you check with your doctor. Different meds need time to build up in the system (typically non-stimulants), so that might be handled differently.