The short answer is: yes, you are right, a course on modal logic would be the one that probably will relate a little to a philosophy of religion course (it will help you understand e.g. modal ontological arguments).

But I think it is worth saying a bit more. I'd be just a little worried if one of my first-year students said "I'm primarily interested in the philosophy of X" for any X. After all, philosophy is a subject where topics don't compartmentalize easily but connect up in deep and unexpected ways. Beginners should be exploring widely, and leaving themselves open to being gripped by all kinds of problems -- what I like at this stage is a student who says "the philosophy of Y is really exciting: that's what I want to do " one week, and then comes back three weeks later and says "wow, this philosophy of Z course is amazing".

And I'd be particularly worried if someone focussed too hard too early on a small area of applied philosophy like the philosophy of religion. This is a pretty narrow specialist area, which not all philosophy departments even think particularly worth teaching (mine doesn't). So, for the moment, do keep your interests wide! And then it is probably a good idea to do a fair amount more logic, as that will keep cropping up as useful background which is taken for granted in work across a range of areas of philosophy.

If you want to work eventually in the philosophy of mind and language, then much better to do some courses on scientific psychology, neuro-biology, and linguistics.

"Real" philosophers argue for nearly every position articulable! But I think the kind of issue that is most likely to come up among philosophers and other academics about such programs is more likely to be about resources. Resources for higher education right now are extremely limited, so judgments about the money required for academic positions and operating budgets to sustain such programs must always be made in the context of competing needs and demands from other academic units. Administrators must always confront the very real problem of where the scarce resources will bring the best value to the institution.

Moreover, different institutions have very different identities and missions. For an institution mostly dedicated to providing the kinds of education that will advantage their students vocationally, for example, such programs arguably do not fit well into that institution's mission. Where liberal studies is the institutional mission, then such programs would seem to be more viable within that institutional context--but again, they also compete for resources with more traditional disciplines, which the institution obviously also has a stong interest in supporting. Different academics will disagree about how to "rank" different disciplines in terms of their importance to the institution, and in these debates some of the more thoughtful criticisms made by opponents to such programs deserve to be heard. But then, many academics will make very different criticisms of the two disciplines nearest to my heart: Philosophy and Classics. Do colleges and universities really need these disciplines? I think so...but everywhere I have taught, I have had colleagues who thought the resources required to sustain these disciplines would be better spent elsewhere. It is because of decisions like these that we pay the big bucks to administrators!

I suggest:

1. you talk to the philosophy professors at your school and ask them lots of questions. Hopefully, there is someone that who has a good sense of what it takes to get into grad school in philosophy, to succeed, and to get a job.

2. you explore websites at some PhD and MA programs. There is also some useful information at http://www.philosophicalgourmet.com/

3. if you remain interested (as I hope you do!), you consider putting off graduation one semester and taking more philosophy courses. I fear that only one course in philosophy will take you off the radar at many programs (I suspect it would take a lot--e.g., very high GRE and GPA--to get some PhD programs to consider you, when they have so many applicants that are philosophy majors or even have MAs in philosophy).

4. you consider applying to MA programs in philosophy to strengthen your background (though it will still help to have more courses in philosophy to get in to MA programs).

5. you will need a polished writing sample with a philosophical argument in it and you will need at least three letters of recommendation (and I think at least 2 of them need to be from philosophers).

None of this is meant to dissuade you, and your outside reading will be helpful (it's just a bit hard to make it evident in an application).

I hope this helps. And good luck!

I certainly think that high school juniors and seniors can learn the basics of critical thinking, ethics, and philosophy. I have breakfast semi-regularly with a teacher from a private high school who teaches philosophy to his students. He'll be teaching Plato's Republic to his seniors this year. So, I do not doubt that high school students have the capacity to comprehend philosophy.

However, it has also been noted as far back as Plato's Republic that older students are better equipped to study philosophy. This claim also seems correct to me. Even most college age students lack the life experience to understand the importance of philosophical issues. In contrast, I once taught an ethics class to 30-40 year old nursing students.... this was an unusually positive teaching experience since they took the course very seriously and understood its relevance.

My biggest concern for you would be whether there are any jobs available to teach philosophy at the high school level. It is hard enough to get a job teaching philosophy to college students. I would guess there are far fewer jobs to teach philosophy in high school.

I think it is difficult for most people to learn much philosophy without the benefit of some sort of class structure. Your best strategy would probably be to find a mentor or a group of philosophical inclined friends with some grasp of philosophy who would be willing to read and discuss important philosophical texts along with you. I would also recommend auditing a couple of philosophy courses when you get the chance.