I am not 100% sure, as far as I remember you need to complete the dildo practice at the office, then keep teaching sports and changing with Rachel and Sally, this will spawn an event in the shower were Rachel will get mad at Sally an then you will be able to use the dildo. During the punishment try as follows:
- Order her to strip naked.
- Position her with hands above her head, do a body search and use the camera to take pictures.
- Bent her over the desk and give her a paddle spanking.
- Change to the headmaster.
- Put her over the knee and rub her pussy.
- Have her on the headmaster’s lap, and spank her while facing you.
- Put her in the diaper position and insert a dildo into her vagina.