I would suggest doing the following:
Set a good example of avoiding sin and seeking virtue in your life. Make mass and confession, Lenten fasting, serving others and other faith practices priority.
Get involved in your church teen group. If there isn’t one, talk to your pastor about starting one. Tip…it has to be fun…plan social events, include faith in those events.
Third, don’t lecture, argue or push. If you have a teen group, invite friends. If they may resist joining the group, start by inviting the to a fun event with the group. For example, they might like to go to an overnight retreat and can then see for themselves how great it is. If she needed be says they aren’t interested, respect them and talk about something else. They may come around if it feels like their idea, which it never will if you are pushy.
Finally, be mindful that your primary job is your own development. Seek friends who are already practicing Catholics. It is not your job to convert your liberal school. If one or two join you in your faith practices, that’s a great achievement. sometimes we want a huge oak tree but only are able to plant a seed. Be mindful that your time differs greatly from God’s time. Plant your seed and trust God.
If people are not open or interested to increasing in faith, pushing can backfire. But if you are practicing Catholicism, it is contributing to your success and happiness, and you still have other fun activities and interests, others will want what you have. If all you talk about is religion, you will annoy people…find balance.