When we say Autism Spectrum Disorders (ASD) interventions, it isn't necessarily somewhere you go to get. If the school won't help, the only ones you can "do" will come from YOU. It's changing the way YOU do things to help him cope. You mentioned on someone else's thread that you changed the way you handle meltdowns when you realized he's a victim of his own lack of coping skills. THAT is huge. Now that you recognize that, you need to figure out exactly what his "lacks" are. I can tell you what I have done to help my son that have helped a lot.
I don't use words like maybe, later, some other time, not now, etc. They are vague words that throw a concrete thinker off. If I mean after dinner, I say after dinner. If I mean another day, I tell him which day. If I mean a specific time, I tell him a specific time. There are times when I don't know exactly when and then I have to explain to him in detail what I mean by later, for example.
I don't expect him to "change gears" immediately. I always give him a reference point of when I want something done or I give him a time reference. What I mean is if I want him to go fold his laundry, I tell him "When this show is over I need you to go fold your laundry" or "When you've finished eating, you need to go pick up your toys" or "You need to get off the computer in 15 minutes" (followed by reminders ever 5 minutes). The likelihood of him following through are a lot better if I allow him to "finish" whatever he's doing or give him a chance to process my request. Kids on the spectrum have a REALLY hard time changing their mindset and transitioning from one activity to another.
Another thing that has helped other parents of younger kids is picture schedules. They can be simple check-off type or remove-when-done type but they need to be visual. Put the schedule up at the beginneng of the day so he knows what to expect throughout the day. That could eliminate some of the anxiety and uncertainty.
You might also want to have him evaluated for sensory issues. A GODD occupational therapist that has experience with young kids can make a huge difference. They can see if there are any sensory things that bother your son AND they can figure out what kinds of sensory things your son craves. My son can't handle certain fabrics, certain noises, and certain kinds of touch. He seeks oral stimulation (chews things), certain movements (spinning, rocking), etc. There are also some things, school related, that he can't do that I never would have thought of.
Good luck and keep checking back. To help, please DO get The Explosive Child book. The biggest help for me was when I stopped assuming why difficult child 1 was doing what he was doing. That book explains how to go about finding out how your son thinks. Asking him "why" he does or doesn't do something in a very calm voice and accepting his answer as HIS truth showed me how very differently difficult child 1 thought. It was absolutely amazing AND showed me exactly why he was having so many troubles.