Most Helpful Guy
The results of this night is really intriguing my night; I mean, on one hand you have the psychology of teacher being more mature / higher status / etc.. and on the other hand, more strict, etc.. So this is gonna be really interesting. Hope it turns out well.
As for the outfit, I'm not a fashionista by any means but I think you could turn this into a great addition to your night by going out with your friend around the town. Maybe you guys can help each other with your costumes or find some guys who would be your board of judges, hahaha.
My idea of the sexy teacher outfit would be more stern/professional; think hayley atwell in captain America. You know your hair best but I'd suggest a pony tail look unless you're gonna go all out, in which I love it when a gal goes to a professional shop to have her hair crimped (something about it is just so alluring). And take this other guys suggestion of some glasses, fucking sexy. I'd probably vote for the teacher, just saying..
Are there any bets on the line? lol