If it is possible at your school try to take biology, zoology, botany, and or environmental biology/science. Science programs vary from school to school and state to state. Anything that teaches you about plants and animals would be recommended.
 In some areas there are many opportunities to volunteer or visit places that aid wildlife. The animal shelter often has to rescue wildlife that has been injured in someway. Many zoos, aquariums,and arboretums large and small, have an educational office where you can inquire about behind the scenes tours and volunteering, as well as some forestry offices. of course the local library has resources for you to learn about subjects on your own.
Good luck!