Onna Kyoushi

From JShoujo Scans:

Kyoko's a recent graduate who just began teaching at a local high school. Being a new teacher, she spends her days battling with the ups and downs that comes with the job. But one day, she notices that a student of hers, Sakurai, has been paying her a little too much attention, and when they wind up being in the same room after school....

also include:
1) Secret cocoon
about a girl who starts to like her deceased boyfriend's brother
2) A caress
about a girl who is in relationship with a married man and a father (love affair).