You could catch some wild Pbass and Oscars, as I know there are wild populations in Fl. that owuld be cool, maybe a wild gar too. But not an Aligator gar, they get to enormous.
If its a classroom tank, I'd think a native setup would be the most "educational", as well as raise awareness of local fish species/populations/etc.
You might be able to house a small schoal of Black Crappie, and/or other sunfish species, golden shiners, maybe a FL gar, warmouth. I've never done a native FL tank before so I'm not sure which species can and can't be mixed, so keep that in mind...just tossing ideas out there.
non-native invasive species. depending how old your class is. make a stocking field trip out of it. and go collect them, and make the whole thing educational. we did that in HS, was alot of fun. teacher had a baby pool instead of a big tank. and we collected natives. was a fun time, and got to see the critters everyday in class we had caught.
I kept the non natives all last year including oscars, midas, and jaguar.... once fish started pairing up there was no peace. I still have the oscars and a couple female midas, but thinking about other options as well.