do you have to put ur child in preschool ?

So my baby is 2 .. i'm thinking about school for him already but i don't want to put him in preschool.... Just go straight to kindergarten when he's 4. Is that okay? or they HAVE to go to preschool??! i live in california by the way... i don't know how this school works.. i went to preschool but idk if i needed to go or my mother just put me in their so she won't have to deal with me lol any new moms know how this schooling goes when they first start?