First of all, I'm really happy that biomedical engineering interests you, since it's what I do and I love it!
One of the interesting aspects of biomedical engineering is that nearly every traditional engineering discipline can be applied to human medical problems. As a result, all aspects of engineering can be found in some form in the biomedical arena. What this means for your specific question is that CAD, electronics, manufacturing and polymers all have biomedical applications and analogues. In practice, most biomedical engineers will end up specializing in only one of these areas, or even a totally different one not offered in your high school.
Your high school program is likely trying to expose you to a range of engineering experiences so that you'll get a taste of the possibilities of a career in engineering, while at the same time making the material appropriate for a high school junior curriculum. The program does not sound specific to biomedical engineering so the examples and assignments will likely be based on more traditional material, although that will depend on the teacher and text and other factors that I can't judge from your message. It's really a luxury to have engineering coursework at the high school level, so you are very fortunate to have this option and should be careful dismissing it. That being said, if you really think the program will turn you off from engineering and you can get the important math and science subject matter in other ways, maybe you should not participate. I really don't have enough information to make a more specific recommendation, so I've tried to highlight the key points for you to consider.