Get him help sooner rather than later. I have ADD and executive dysfunction, which was undiagnosed until I had a breakdown my first year of college and failed a class my last quarter. My grandfather is a psychologist, so he tested me and has been treating me using neurofeedback. It’s been extremely effective and I’m so much happier with it instead of meds. I would highly recommend neurofeedback for treatment of ADHD - just make sure you visit a psychologist, not an occupational therapist, with several years of experience with neurofeedback.
Keep in mind that your son will need nudges and support in staying on track - that’s one thing that I try to get my family to help me with. I can focus better with the neurofeedback, but I have to work really hard to stay organized and on-track. It’s not one-and-done, you’ll need to check in with your son from time to time to catch anything he might be missing.
Remind him that things will get better. He’ll have bad days and good days, but things will get better, and he’ll learn how to manage his attentional issues. Ask him how you can best help him; he’ll appreciate it and will know that you are supportive. Also make sure to assure him that there’s nothing wrong with him - he just needs some extra support from time to time. Sometimes my mom makes my ADHD out to be a bad thing, and I don’t appreciate that because I know its not bad, it’s just something I have to work on managing.