Children should have their television time limited. Encourage your children to explore their environment by playing outside or using their imagination as they play inside instead. Instead of family TV time, fill your child's evening with family reading time. This will allow your children to develop additional skills that will benefit them educationally, as well as reinforce the fact that you value books and the ability to be a strong reader.
Teaching your child to be a good student starts with developing a strong work ethic and good study habits. As a parent you can model these for your child and being to instill them from a young age. Doing so will help them be successful academically and likely in their career endeavors as adults as well.