How would a 15 year old boy start looking into acting?

At school I haven't taken any performing arts subjects as i feel it's too big of a risk (I know it's a risky business) to throw away other subjects I'm talented at that I'm doing very well in. When I used to do drama, my friends said I was very good and I was given a lead role in every one of our little plays.

I attend a performing arts school called 11th session which I feel would be a good start for me. I'm mainly a musician and I play the drums but there is a huge acting and drama group there that I've been thinking about joining, I'd be the first boy, but I'm confident so it should go down fine at first. I don' mind where I start as long as I get the chance to actually take the talent somewhere, if ever in my life I made it to TV, that would be awesome!

I'm more of an "up front" person when it comes to acting, I love to move around and be loud and be my own person or character. I've been in 4 productions in my primary school. I have a very slight but still recognizable lisp that has slowly got better with age. Some people get lisps as a child and they go when they get older, plus if I put an accent on the lisp seems to become almost insignificant.

I have an aspiration to become some sort of actor. I love movies and TV of all kinds but mainly action/adventure style films. Some series' that I love are Breaking Bad, Game Of Thrones, The Office (US and UK) and The Walking Dead. I really love any kind of movies but my favorites are things like The Lord Of The Rings (including The Hobbit) and anything that DC or Marvel brings out. I don't think I'll ever end up anywhere near that scale of acting but I would like to start somewhere and at least try to see where I get.

To summarize, and sorry for the wall of text, I would just like to ask how I could further my aspiration. I was thinking of maybe doing some kind of series on youtube with friends that I could refer to if I ever look for an agent, to show at least a bit of experience. Thanks :)