My Highschool Bio teacher had three ferrets that were awesome to watch and play with. The older one simply ran around the classroom full-bore, smacking into anything and everything, he was so blind.
The younger brother spent most of his time beating up his younger sister and occasionally dragging her across the room, while she struggled and protested.
They were definitely a distraction, but I don't recall a single person who dreaded going to her class - it was my favorite class, by far; and we had tons of other great classes, too. I personally liked Physical Science (our teacher reminded me a little of Mr. Wizard), Physics (our teacher built all of his own contraptions, such as low-friction carts for conservation of momentum and energy practical, as well as stuff that would blow up or cause awesome laser shows, which were used for speed-of-light calcs) and English (one was an ex-Eagles cheerleader who taught us, well, I don't remember what she taught us, but I was always on-time! The other English teacher was a sarcastic, "mean" old lady with a razor-sharp wit, who only hated you if you were disrespectful.) Out of all of those classes, I still preferred going to Bio, mostly because the ferrets were so entertaining.
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With all of that said, Ferrets STIIIIIIIIIINK! No matter what you do, they stink. If you plan on having girls over, you'll be hard-pressed to mask the stench!