A female substitute fills in for a class, and the guys find her extremely attractive and start fantasizing being with her throughout the day or in other classes, causing mayhem.

No genderblending please. The teacher could be an already female nation or just a normal woman. Guys being guys and womanizers. Go crazy and have fun with it.

Bonus:
-she doesn't like France at all.
-Either Spain, Romano, or Denmark come close to crossing the line.