Feeling unprepared is very normal. Our story is very similar to yours. My girls were also overwhelmed with home work and our oldest had a mentally abusive teacher. The system can tear your children down quick. It takes a long time to repair the damage.
I home schooled our 2 daughters from grade school through high school. They have both gone on to college. I will start kindergarten with our son this fall. We are military and moved a lot so this life style worked very well for us.