Your step-mother will catch you as you stroke your dick instead of studying. She will become furious and wants to punish you right away... She just got a phone call from your teacher, that your grades are worsening, and she says it is because of your hormones and wayward penis... She will lock your dick with a chastity device and blackmails you, that if you cannot correct your grades then she won't open your cage for a year ... First she will lock you for October, to check your improved results and IF your grades will be fine, she will open the device once a week to let you cum for health reasons... Well if i would be in your place, i would start to study fucking fast !