Illegal use of hands or nothing?

[Newbie Scott]

I have heard different answers to this one so let me know what you think. Since there is no 5 yard rule in High School can a defender basically block a receiver all the way down the field? I think no, but some have told me he can chuck him all the way down the field until the ball is in the air. According to rule 9-2-3d a defender cannot contact an eligible receiver who is no longer a potential blocker. Now I would let the defender basically chuck him off the line but I think once the receiver is on the same yard line as the defender he is then off limits and if the defender hits him before the ball is in the air we have illegal use of hands. Maybe I am making this harder than it should be so please help me out.