Seeking advice for my young, amazing, neuro divergent son

Hello to all who are reading.

I'm writing today seeking first validation and second advice for ways to cope with autistic fatigue and burnout. 

My son Abel is on the spectrum. He is 7 years old and verbal. He got his diagnosis at age 4. In fact his daycare had prompted us to get him evaluated at age 3. It didn't take long for the diagnosis, approximately 9 months. We have embraced and encouraged him in every way that we know how. 

He has a sister who is very close to him in age, she is 6. She is neuro typical. They are very different. I never compare the two as they are both amazing and wonderful in my eyes. 

Fast forward to now. Abel is in the first grade. He has an IEP but spends the majority of his time in a typical classroom setting. He attends speech and occupational therapy at school also additional help in reading outside of the classroom. I pick him up an hour early on Friday to attend OT at an autism services center. 

His teacher has been expressing to me for a long time that Abel falls asleep in class. At first I thought maybe we should adjust his bedtime. So I did that. He and his sister got to bed at the exact same time every night, same bedtime routine. Well, that didn't solve the problem. The teacher would continue to message me saying he is still sleeping in class. So I thought maybe he is on his tablet too much before bed. He is a gamer at heart. He is still young and enjoys Roblox. I myself am not a gamer but I find it's a way I can connect with him, so I enjoy it when he gives me a glimpse of his life on Roblox. He doesn't have to worry about stressful social interaction or masking his autistic traits on there. Anyway, I have tried to limit his tablet time before bed due to falling asleep in class. Nope, no results. Teacher still telling me he's always very tired and I should know.

I must tell you, Abel is a sweet, sensitive, rather shy boy. He has never cried to me about not having any friends until this year. He has cried out of the blue saying and I quote "I just want someone with me at school" I asked him what he meant and he said "a friend". I went so far as to throw him a birthday party, karate themed as he is in karate. I sent invites to the whole class. Not one student showed up. He is in a class of 20. So as a mom this hurts because I want to help but I can't go to school with him. 

I had a couple of meetings with his teacher in which she expressed concern about his reading level and sleeping in class. I thought this was the perfect time to express my concerns to her about him feeling isolated from his peers. Making him dislike school. Maybe she could encourage some mingling amongst the children. 

When we met it was half way through the school year. As we are talking she is telling me he's very quiet and his behavior is great but he does better in one on one settings. I was not shocked to hear this as it sounded very much like him. Then I mentioned he's been feeling lonely and she reacted as sympathetic and quickly changed the subject. Then I had mentioned him being on the spectrum and she goes "oh you say he's on the spectrum, ok" then again quickly changed the subject almost like she's uncomfortable with talking about it, like it's not COMPLETELY RELEVANT. I'm not sorry he's on the spectrum. I don't throw a parade about it every time I meet with someone because it doesn't define him as a person but I certainly take into account that he has a different set of needs than the average child. 

Anyway the meetings are getting me nowhere. I don't feel heard by his teacher I don't think Abel is having an easy time at school. Then I got another message from his teacher literally as I'm in my car in line at school to pick him and his sister up. She messages me and says "Abel is very tired he's falling asleep right now" so I politely message her back saying thank you for letting me know.

Then I got to thinking when Abel was being diagnosed in the early stages, they would always ask me if he tires easily. Then I looked it up and discovered something called Autistic Fatigue/Burnout. I read about it and realized this is probably what's going on. 

Does anyone with autism have any experience with this? What should I do to help and get his teacher to understand?