Most of the time, most people will listen to their own biased beliefs than the truth. Why? Because people don't like to admit that they were wrong and will believe anything that tells them they are infallible.

For example, you started to believe that cannabis should be legal and is relatively harmless after you started using it, right? Sadly, whether or not that's true, it does make your opinion biased.

Like peacenotprofit said, I don't think you'll be able to convince your dad. Just bite your lip while under his roof, stay in school, and prove him wrong by becoming a big success in life.