What type of academic training do I need to become an engineer?

Academics are a big part of engineering, particularly as strong foundation in math (calculus) and physics, and other sciences depending on which field of engineering you're interested in. I also agree with Rob (above), technical writing is important because you need to be able to effectively communicate your engineering efforts and findings.

Most engineering is based on problem solving and creativity, so I also recommend pursuing "hands-on" training/experiences to see if engineering is a fit for you. Such opportunities are endless, but a few ideas... building a popsicle bridge, working on a soap box derby car, participating a robotics competition, designing a simple circuit board, working on a chemistry investigation (with a teacher!), building a team website, creating a small app for a cell phone. Check with your math/science teachers or guidance counselors to see if they have recommendations for local events.

For high school, I would recommend that you take as much math as possible. An introduction to physics would be advisable also. The college curriculum is fairly well established and would depend on your focus, electrical, structural, environmental,..... At some point a technical writing class would be helpful as that seem to be a missing skill at the "entry level"..