It surprises me how much my attitude to this post is "15 years from now, is it really going to matter that much what you did in high school to get into college?" AFAICT, academics are not that strongly related to long term career success, and that in the longer term, traits like conscientiousness and skills like working with others end up being more important. I wouldn't recommend to my child that they try to signal their worthiness to colleges and universities at the expense of actually acquiring skills.

I was nodding along here until the last sentence. What you did in high school will usually cease to be relevant after some time, while the signalling value of a sufficiently prestigious college remains. You can usually make up missed learning opportunities from high school, such as the molecular biology course given in the example, whereas the window where your activities will be relevant to college placement is much narrower.

For a sufficiently conscientious student, the value of high school may be primarily what it gives them the opportunity to signal, rather than what it gives the opportunity to learn, aside perhaps from lessons of a social rather than academic sort.