Preschool, also commonly called nursery school is currently an optional thing in the US. There has been talk of making it mandatory. The whole concept of preschool is controversial, with some feeling the child who doesn't go is going to be socially deprived while others believe it is just another form of daycare or that children are not ready for formal education at this tender age.

Typically 3 year olds go for 2 days a week for about 3 - 4 hours. 4 year olds go 3 days a week for the same amount of time.

Usually potty training is required in order to attend.

Tuition is high, hundreds of dollars a month at times, and in my experience by the time I dropped the kids off, and got home again it was time to go pick them up.