Or, in this case, adults.

A special kind of "adults." I went to college and grad school in two different towns. Each college had its own culture of fun. The kind of "fun" that the colleges condoned occurred in a sheltered atmosphere, and would have been utterly off limits to the adult residents of the surrounding towns.

> The kind of "fun" that the colleges condoned occurred in a sheltered atmosphere, and would have been utterly off limits to the adult residents of the surrounding towns.

... What kind of "fun" is that? The only thing that I can think of that would be off limits to non-students is literally illegal activities that students shouldn't be doing either.