Individual states have different laws in terms of age cut-offs for starting school, but generally, children can start kindergarten when they are 5 years old. They do not have to, but schooling of some sort is compulsory when the child turns 6 years old.Starting a child at 5 or 6 is a decision that every family should be able to make for their child based off of several factors, including social, emotional, physical, and academic readiness.