How can I make friends?

Im not content with my lack of friends and I’m struggling to change that. I’m nearing my last year of highschool and I really want to enjoy the time I have left as a young person with little to no responsibilities. I go to an all boys religious school which makes it difficult for me to make friends through school because I can only interact with boys on a daily basis and majority of them are very very similar and I lack a lot things in common with them. I’ve tried many times to make friends at my school but time and time again it’s failed because we’ve never had enough in common. I’m not terrible at social situations but I’m not confident enough to just strike up a conversation with random people out and about. What are some things I can do so that I can find and make friends?