You should do your best and try to show through your actions that being Shi'i has made you a better person, and try to be respectful even if you are being mistreated. I recommend avoiding debate about it (unless your family is open to discussion) - usually teenagers do not win arguments with their parents, and you are socially and financially disempowered at this time in life. Debates about religion are often about other subjects too, such as identity and control.

Beyond that, just try to do your best to learn and hold to what you believe; if you need to do taqiyya, you can. 

I can empathize with this since I started to practice Islam when I was 14, and it was not welcomed in the household. So I used to study Arabic and other things at school (I hid books and read them during class), and do wudu in the closet. I am not recommending that you stop paying attention at school, but I am just saying that teenagers find a way to do what they feel they are called to!

While it was difficult for me at the time to be disallowed from associating with other Muslims, I also realize now that being on my own forced me to formulate my own beliefs and understandings rather than just going with the crowd, and this was helpeful in the long run. So patience is a virtue. (Of course, nowadays it is somewhat different with internet, where we can access religious media of any type easily)

Inshallah when you are older, you will also have more freedom to practice and learn more, especially if you have the opportunity to go to university. Also, it usually gets easier to make your own decisions as an adult, when you have your own finances and your own life. 

I am sure others will have advice as well!