First of all, every school has a different selection method. A little more information would be handy. I see you're Dutch, most likely you're going to AIS, since both KLS and EPST (the only remaining flight schools) won't let you get your medical until you've passed all the tests.
One thing in general: You're 17. All the other guys are probably 22/23, have their bachelor and/or degree and much more live experience. Sounds discouraging, but it's not something that you can't do anything about. It's very important that you're able to compete with your fellow aspirant pilots. For example, in a group exercise, stick to your point and convince the fellas that your point is the best. Also, listen to an others input and use it for the group process.
In addition, where a suit, be polite (but don't overshoot it) and be focused.
Good luck!