About to switch my sons school before this baby is born!! 😡

I am so upset 😡😡😡😡 

My 5 year old son has had a virus and out of Kindergarten all last week. He just went back today and his dad took him (we are divorced) and it was the Halloween parade and also dress down day. He goes to catholic school. So the parents were allowed to come see the parade at 11 and my son is one of two kids in the class without costumes on. And my son loves Halloween more than anything and missed trick or treat since he was sick on Friday and really looking forward to today. He comes out and is parading around with the class crying hysterically that he doesn't have his costume. I went to pull him out of the line and call him down and his teacher cut me off saying he's fine and let him continue walking around crying. I called my ex and flipped thinking he forgot his costume and he said no it's in his backpack. My mom was with me and told the teachers aide and she took Nate to get his costume on. They come back after the parade is over and they're sitting on the gym floor for pictures and she comes over with an attitude and says "it was in his backpack. It's his responsibility to keep track of his things if they're in the backpack " and storms away! I was shocked. The teacher and the aide are both in their 50s and didn't think to check his backpack? He's 5. And it was a special day. He's been in and out of the hospital all week, and goes back on his first day to get upset. He was hysterical and embarrassed . I tried to say goodbye to him along with other parents afterwards and the aide got in front of us and put my son back in line and turned him so his back was to me. They were rude and insensitive to us and my child. And this isn't the first time. I want to put him in public school at this point, I think a half day would be easier on him and he still has time to make friends. My ex wants to wait until next year and thinks I'm going to put too much stress on him changing schools. He doesn't have any friends there and at least he went to daycare with the kids that are enrolled in the public school. He also came home crying a few weeks ago and said the teacher told him he wasn't special. What do you ladies think? I feel like regardless of my ex I have a right to pull him out of what feels like a bad school.