Taiiku Choukyoushi ~Kichiku Jugyou Bloomer Yuugi~

Main character loves girls in bloomers more than anything in the world. He gets a qualification as a physical education teacher to be always surrounded by them. He gets offended by arrogant attitude of Maria girl, so swears to have revenge over her. The first step in it is making a photo of a shy girl Shinobu masturbating in the classroom to blackmail and train her.

[From vndbreview]