Title: Temperature Rising
Author: Souya Himawari
Media: Just Manga. Happiness Recommended is technically the first in the 'series', however Temperature Rising is strong enough as a stand alone.
English Release: Yes. It's available from Waterstones.
The description of this novel makes it sound dirtier than it really is. Prostitution is a feature here, but Temperature Rising is actually quite light on the palette. Some of the scenes are steamy and the general storyline is a little overused. This manga sits somewhere in the middle ground of hard and softcore.
Finally, if you like your school settings, then this a definite read.