You're young, so it's a bit early for them to subject you to a phsyc test. But doing these camps and youth programs will help mature you and grow you up some to better handle that stuff when it comes time, you'll be a much much better position than a recruit that graduated High School but hasn't been through any of these programs that you will of gone through.
It's a good career choice if you're happy and content with the work, pluss you'll spend you're summer having some fun out somewhere and also feel productive about advancing skills you can use for your future. It is a thankless job though, don't expect unanamouse praise and respect for your decision, many people simply don't have the mental, physical or bullock strength to serve the public thanklessly while under constant scrutiny. Law enforcement is a kinda tough job, 70% of people support you, 70% of people don't trust you, and then there's the real loons that want to take pot shots at you while you're sitting at a school making sure nobody runs over the kids. Just remember, it's a position of authority, it both comes with some respect and authority but also a ton of scrutiny and accountability.
Getting on the early track will help fast-track you into a job when you graduate school, and it'll also be an incentive to do well and graduate on schedule in school, something most people lack until they're already done and graduated. These program's purpose and intent is to take young people like you who are far from perfect, but with honest good intent in them. They mold you by giving you the the skills and resourcess needed for viable and prepared recruits to join the police force.
They'll keep you busy too before you're of proper age to serve, if you get proactive with them and they like you, there's usually always some event going on every weekend in the summer that they need a cadet to help with, even if it's just managing traffic. It'll keep you out of trouble, probabley get you into a few venues for a few hours for free, and make connections with those already on the force and working in it.