Hi, I would strongly recommend that you focus on the fun in learning by reading with him a lot and doing hands-on types of learning. I wouldn’t make schoolwork and homework a battle ground. I’m starting to believe that we need to find the right environment for the adhd kid, not force the kid to fit into a particular environment. This may not be an option for you but I would also consider sending your son to a school that is less traditional. Sitting in a chair for several hours a day and focusing on tasks that may be painful for him is not productive, in my opinion. Schools that allow the kids to move around a lot and that are very hands on serve adhd children better. Homeschooling is also something to consider down the road.
If he must stay in his current school, you should ask for special accomodations like allowing him to stand up at his desk or take a walk down the hallway several times a day. My advice to you as the mom would be to give your son as much outdoor time as you possibly can. This is calming to an adhd child and they desperately need to exercise/energy outlet. Also figure out the time of day when he is at his most calm or focused, and then reward him for every 5 minutes that he can focus on work. At 7 years old and just entering 1st grade, the academic demands should be very low anyway.