The meltdowns can be because of the changes, having to get used to a new routine, structure, all the noise, lights, etc. A kindergarten classroom can be overwhelming. I just saw Temple Grandin and she goes on and on about kids in the spectrum and how important building their social skills are. You have to advocate for your child at school because my experience with school has been awful! THey do not want to give the services that can help. You have to ride them like a bull! Every school year starts the whole meltdown again, new teacher, new classroom, etc... after a few weeks of adjustments he is ok. Go in the classroom and see where he sits, maybe there is something to stimulating, maybe he needs to sit by the window because the lights are annoying him, that was one of the things that Temple Grandin said that flourscent lights are the WORST thing in a school, you can put the child by the window with a desk lamp with a regular light bulb. Maybe he might need to get up and move around periodically, pulled for OT, social group, does he have an IEP? Send him with fidget toys, the teacher should work with you regarding this. THink about how overwhelming this all is, hanging up coats with all the kids and their talking, switching from task to task, I know my son needs ample warning for transition and what is going on. If transition is an issue for him, maybe he needs his own picture cards on his desk. After school maybe take him to a park or somewhere he can run and get that energy out so his meltdowns are not so severe. Good luck and remember we are all here for you! We have to be patient when they cannot!