In Kindergarten Cop 1990, John Kimble(Teacher) makes kids in his class take a nap.
Do teachers in kindergarten schools prepare kids to sleep?
Yes. Nap time is a real thing in schools. But some places have done away with it, and some have brought it back. It's not universal. See http://www.ktbs.com/story/26103533/new-nap-time-policy-for-kindergarten for example.
There are studies that are for and against kindergarten nap times, so no single expert to listen to.
It was more common back when the movie was made.