http://www.mangago.me/read-manga/ashita_no_kimi_wa_koko_ni_inai/
http://www.mangago.me/read-manga/pink_to_mameshiba/
If you have already read these two then reread it :3
You've probably read all these and school stories are not my favourites, and I'm not personally crazy about the power dynamics between teachers and students, but there are a few exceptions:
Does doctoral student x professor count, even if the protagonist has a crush on the student, but isn't the professor? http://www.mangago.me/read-manga/koi_o_kataranai_kuchibiru/
Similar theme, but more sinister (and not a doctoral fellow):
http://www.mangago.me/read-manga/mujihi_na_otoko/
How about when the student x teacher relationship is not the important thing about the story? http://www.mangago.me/read-manga/emotion_circuit/
Or when the lover relationship happens long after the schooling is over?
http://www.mangago.me/read-manga/goodbye_lilac/
http://www.mangago.me/read-manga/aozora_no_sunda_iro_wa/ (one of my absolute all time return to favourites)
And, finally, the one that's the most conventional of the bunch:
http://www.mangago.me/read-manga/abiru_junjou/
soo any yaoi recommendations with student and teacher relationships?