Ask HN: Need help with keeping my child's online school schedule

I have been grappling with this issue for sometime now that I finally decided to post it on HN to solicit feedback/suggestions. Essentially, my son(diagnosed with Autism) suffers from ADD. This has hampered his executive function long enough such that he needs constant reminders to log in to class without incurring penalties for tardiness, needs constant supervision for Homework. There have been instances where he forgot to log in to his designated private lesson and we had to forfeit the class all-together. But once he receives the prompt and he is able to "initiate" the task, he is able to focus long enough. But, now that he attends a "Full-time" online high school(remind you NOT a homeschool), he needs to have 100% attendance and cannot miss or be late to login to his class.

I do want to preface it by saying that our son was diagnosed early on in his life and has had intense therapy for OT and social skills(there has been minor improvements), but being in high-school now the real life skills are lacking. I am looking for tools/processes to improve his executive functions. Perhaps a reminder system, iphone based alerts(he does wear an apple watch) or some kind of visual aids. Anything free or paid(Apps/offline paper based systems) is fair game here. Time is of the essence and I thank you if you read this far.