the only time I've ever heard of students taking naps (and not slacking off) anywhere would be in Kindergarten in America, and perhaps some European countries.
However, if you want to persuade people of the importance of children taking naps, try these resources.
Naps Help Your Memory, New Study Suggests
Nap Time - Pew Research Center
NIMH · “Power Nap” Prevents Burnout; Morning Sleep Perfects a Skill
Napping: it's not just for toddlers anymore - The Boston Globe