What is my activity level, sedentary or lightly active, help?

If what you described is all you do I would say it's pretty sedentary. If you belong to a sports team or play outside a lot, swim etc after school or on the weekends then that would make it different. You have no choice but to be seated most of the day at school - it's what you decide to do with your time that you are in control of. Walking through a shopping centre won't cut it for what you need on a daily basis. You should be getting a good 30-60 minutes of brisk cardio activity 4-7 days a week where your heart rate is elevated and you are breathing more rapidly. (That doesn't mean a thrilling movie or video game ha ha ha). The point is, if in doubt, bump it up. It can't hurt to do more but it can hurt if you aren't doing enough. Join a team/club or just get outside and kick a ball around/ride your bike. Hope that helps.