My DS2 is excelling in AP Biology and loving it to where he might want to keep going with it in college one way or the other. (either pre-med/psych or biochem). I checked the local Community College (we’re in NorCal) and the offerings for bio are paltry. Coursera on the other hand has a mind boggling selection of material that he could potentially study. From a college admissions perspective (UC or private) I wonder if he should focus only on those courses that offer a certificate to prove he mastered the material. ?? Or should he just study whatever interests him and perhaps center a college essay about the experience of say studying Experimental Genome Science from U. Penn. Coursera seems like such a great resource. Seeking insight as to how admissions teams view high school students digging into it.
As homeschoolers, we use coursera. We don’t pursue the certificates. The courses themselves vary in terms of content and quality. Over all, we use coursera as a supplement.
Another source you might want to consider is MIT opencourseware. http://ocw.mit.edu The advantage to opencourseware is that it is available all the time and many of the courses offer full-semester content with full exam/ solutions. (Again, not all courses are equal. Some do not offer as many components as others. You have to search through them until you find one that offers what you are looking for.)
Hth
I’m in favor of the student studying what interests them. The essay is a good idea because it shows why the interest is there.
There is learning for learnings sake, and then there is appealing to admissions committees.
Admissions committees need evidence…a GPA or an SAT/ACT score shows evidence.
I don’t think in 2015 saying you took some courses will have much of an impact.
But could he take that knowledge and do some research?
I think adcoms want to see learning for learning’s sake. That’s part of what makes home schooled students stand out. As long as you’ve met the other requirements for admission (standardized test scores, etc.), I’d let him study whatever interests him.
@Mom2aphysicsgeek Thanks for pointing out MIT opencourseware specifically. Somehow I had it in my mind that of MIT’s opencourseware was included in coursera. I’ll check it out.
@bopper Yes maybe this will just need to be learning for learning’s sake. I was just trying to find a way to create a two-fer. 
Our older boy is getting admitted to some good schools in part due intense interest in computing that he displayed via hackathons and community college courses in addition to high marks in school, SAT and AP. I’m trying to think what the younger could do to expand his knowledge and show that in addition to marks he wants to go next level.
I am an alumni interviewer and see students doing research over the summer as showing they want to go to the next level. Sometimes this is through a local college or a program. Or see if he can talk to his Bio teacher about doing a research project now or helping him to hook up with someone local do research. It won’t hurt to talk about taking more courses on your own, of course…it shows intellectual curiosity.