<p>I would talk to the professor of the class first. If you’re a high school student, the answer will almost certainly be yes. You may also be able to get your homework graded, depending on the class (if you don’t do the homework, you won’t really learn anything). The prof will be able to tell you what sort of math background the class will assume, and you can get added to the class mailing list so you know what’s going on.</p>
<p>You can see the list of classes at [Caltech</a> 2009-2010 Course Catalog](<a href=“http://pr.caltech.edu/catalog]Caltech”>http://pr.caltech.edu/catalog) and the list of classes scheduled for this term at [Office</a> of the Registrar - California Institute of Technology](<a href=“http://registrar.caltech.edu%5DOffice”>http://registrar.caltech.edu)</p>
<p>From comments made by another high school student sitting in on classes, you will definitely not receive any sort of official credit.</p>