They go to class. Teachers should not be helping students outside of school hours. They should have a life and meet their own needs as humans. For that matter students shouldn't be doing more than 6-7 hours of school work per day, which they already get at school. Students have no need to turn in assignments outside of normal hours, and it's unhealthy to encourage them to do so (this is where uni professors really need to stop setting computers to accept work at midnight. Horrible habit to build that needs to be untaught when people start working).
When I was in university, midnight was well inside “normal hours” for me (mostly by choice, not by crushing workload despite being at a competitive school).