Have you thought about putting him into a montessori? I know it is expensive most of the time, but one of the main things they teach is a love for school.
I have a HUGE problem with public schools, especially in Houston and some surrounding areas. The teachers are not helped by the policys of the board and the children are not being taught to love school. This could discourage your child for the rest of his school days, it happened to my brother. He was Extremely intelligent and a teacher told him he could not do something because the other kids couldn't do it. My mom said from that moment on he hated school, he ended up dropping out at 17 and now has no degree to show for how smart he is.
I work at a montessori, and at 4 your child should have a fun loving environment to learn in, and if the teacher is not happy then obviously the students aren't either. If you can afford it, I would highly suggest that you find a good place to put him, and if you cannot I would suggest taking him out until next year and hope that he gets a better teacher. Maybe even see if you can transfer him to another school.
If you would like info on where I work please send me a message and I will be happy to help as much as I can!
Good luck, and I say a prayer for you!