I strongly recommend Ohitorisama :) an older female teacher falls for a younger male collegue. The guy is Koike Teppei, very adorable <3
Thanks a lot people. Sapuri, Kimi wa Petto, Natsu no Koi wa Nijiiro ni Kagayaku, Ohitorisama. I've already watched them all. Those are really awesome drama. Love them all. And please if you still have some that you know about OlderWoman-YoungerGuy drama. Please don't hesitate to drop them here. It doesn't have to be SCHOOL romance. It's fine as long as there is an OlderWoman-YoungerGuy involved(as main characters). THANK YOU VERY MUCH!
it's not for teens but it's romantic and awesome story ,i like it soo soooo Crazy for you
Last Cinderella Older lady and young man, but it's a love triangle.
Another older woman - younger guy drama you need to check out: Boku dake no Madonna. :)

http://mydramalist.com/japanese-drama/583/boku-dake-no-madonna
check out last cinderella. even tough it's not a teen drama, but for me, i love this drama very much. and for teen drama, i recommend Hana Kimi (rom-com) and Kimi Ni Todoke (a sweet one)