[G4] Is there a way to turn off a router so than no one can log on late at night?

[SKYGRAM]

Hi Gang!

Does anyone know of a way to turn off a router so that no one can use
it after midnight?

A neighbor asked me this question because he discovered that his
children were accessing the Internet late at night after he an his
wife had gone to sleep.

Is there another way than merely hiding a cable of some sort. Could
there be a password approach to the problem?

Bill