Any moms or teachers with advice??

Me

I teach two year olds and have noticed that when we go in for nap that the kids start bouncing around and talking, pretty much keeping each other up. We normally go down around 12 to 12:30 but due to this some of the kids don’t get to sleep until after 1 but wake up a little bit after two which causes some of them to be cranky afterwards. Is there something that I could do to prevent this like possibly making them watch a movie or having a calm down period? Btw they eat lunch around 11 and as soon as they’re done they get their diapers changed and play until its nap time.