Hi F. -
I'm so sorry you're going through this rough patch. It's so difficult to make these decisions for our kids and know if they're right. I have an 18month old. He's been in daycare about a year. But about 3 months ago, he switched classrooms. It was horrendous. He screamed, cried, kicked is legs, hit the dogs, trouble sleeping, etc. I spent most evenings in tears! I set up a meeting with daycare and found out he was nothing like that there, he was great. So I did a lot of research, talked to my pediatrician, and also with his teachers. It seems he was having transition trouble and was taking it out at home. I learned 2 things that made me stop crying (and him!). 1 - this is a phase that WILL pass - it usually takes 6-8 weeks for toddlers to adjust. 2 - create a ritual that is done right after you pick him up. He has been stimulated all day long and needs to "relax" - taking walks worked for me. I also would go to the grocery store. He liked having me "one on one" but without having to interact with me necessarily.
He outgrew this stage in about 3-4 weeks, but it was really hard.
Don't give up - it is important to socialize your children, and if you can do it before they're thrown into a school environment, he'll adjust better.
I was concerned about something you said....the teacher yells all day. This is not normal. If they can't control the children, then they are doing something wrong. I would consider doing some surprise drop-bys and seeing how the class is conducted. You may consider finding another provider with maybe smaller teacher to children ratios.
Good luck!
S. B.