I tried getting work experience in my local park when I was in your school year but they only accepted over 16s cos of Health and safety dribble. Don't do anything through school (useless!) have a look on your local park's bulletin board and look for days where conservation volunteers meet. or have a look and see if there are any nature clubs near you. there are 2 near me and I'm in both. most members are over 60 but who cares. I can be myself without trying to please some thug. the preston club near me gives talks every monday. I'm doing one on Dec 15th about the flowers I have seen this year.