I'm interested in spending the fall semester of my junior year in high school abroad in Spain. I've discussed it with my parents and the such but the hard part/first and foremost step is finding a reliable abroad program online.

I almost submitted my information to Two Worlds United. I later Googled reviews of the program and it led me to this site [askmehelpdesk] saying it was a scam and whatnot.

What I'm looking for is a program that can basically find me a good host family in an urbanized environment and enroll me in a public high school during the fall semester. It is surprisingly hard to find something so simple.

I'd like some recommendations from students/parents/people who have had success/great experiences in an abroad program that is reliable and trustworthy.

Try Study Abroad UK or AFS

I went through Youth For Understanding as a junior in high school. They are another organization that has been around for a long time.

I just graduated from college and I studied abroad my junior year. If I can suggest something, it would be to wait until you are in college to study abroad. If you want to do something now, there are really great summer abroad opportunities but I think your abroad experience will be heightened in college years.
Almost every school I know of have great programs for study abroad, it is great for applying for jobs after college and getting new perspectives on your area of study. (Unless of course you are planning on doing on both!)