Something like 15 minutes break between 45 minutes of each lecture/period would be probably the most logical solution (which many countries implement) so there is at least some chill time instead of just having to hurry class to class. What if you need to 9/11 the school toilet, grab the heavy-arse books from the locker, make death threats to NAFOs on Twitter, or get some xp in Runescape? Maybe kids will be less likely to goof off in class?