Tell your parents you are loosing intrest because you feel like it is being forced on you and you feel it will cause them to shun you till the day they die . tell them you want to study school stuff instead because you want to earn a scollorship even though watchtower preaches against it, and you still want to have fun like a kid should.
din't prepair for the study with bob ever and when he asks tell him you really do not enjoy it at all and it is pushing you away from god.