I believe students are much more homogenic than you find in school (eg dumb people are around) or in joining the military (you meet conservative people).

There are many axes on which to measure homogeneity or diversity.

I don't think you're wrong about the axes for "academic intelligence" or "political outlook". But those are just two of many. Geographic, racial, economic, class (in the European sense), language, culture .. these are all equally valid, and likely to vary more in a university than in a workplace (even in the military).