You can try using positive reinforcement to get your kids to study. But what if that doesn't work? Well then, it's time to try some more medieval methods.
The study ball is a literal ball and chain that comes equipped with a timer. Simply set how long you want your little miscreant to study and attach the ball to their ankle. When the time is up, it'll unlock, allowing them to leave their rooms. Until then, however, it's study time. Or trying to run out of a burning house with a ball and chain time, but let's just hope that doesn't happen.