The question that parents of gifted kids run up against too soon (in my opinion) is when are they ready for college? For homeschoolers particularly, a community college seems a good fit for teens (and pre-teens) who need higher level learning than their parents may be able to provide. Community college (CC) also provides a college experience for kids who may not be sufficiently mature to live outside their parents' home. But without a diploma, how do we hook them up?
In our state, the Youth Options program through the Department of Public Instruction is set up specifically to allow high school juniors and seniors to take community or UW college classes that count toward their high school diploma. Tuition is paid through the public schools and although it's trickier to get access that way, if you have a relationship with someone at your local school, that's a possibility. Prior to that, it would have to be on a case-by-base basis, negotiated between you and the particular school or professor and tuition would most likely be entirely your responsibility.
Our local community college has an entrance exam called COMPASS that all incoming students take to make sure they are placed in the appropriate classes. The COMPASS test is not age-restricted, so if your child took the test and passed it, you could easily approach the registrar and say, "Look, he's working at a college-level. How about you let him take this one class and see how he does?"
There is some question about whether racking up a large number of community college credits is a good thing for homeschoolers to do. It very much depends on what your post-high-school plan is, because there are as many ways to view these credits as there are four-year universities. As I understand it, there are more advantages to entering college as a freshman (priority in housing, more openings available, more financial aid available) than as a transfer student. Each college is different as to which credits they will allow to transfer and who qualifies as a freshman, so it's worth checking with the schools (and potential schools) on your list to see what their policies are.
I was looking into this primarily for upper level science and math classes. Although I've been doing okay supervising Klaus's correspondence-school biology lab and DH said he'd oversee a similar chemistry program, physics and AP level wet lab work would be more difficult in the dining room, as would any math higher than algebra II (at least for me. Less so for dh).
Klaus and Wolfie are taking the ACT in February, so I think we'll wait until we get those results back before making any CC decisions. That should also give us some time to narrow our list of possible schools so we can get some guidance that way.