Does being rational mean having faith in reason?

I'm a high school student in a religious school. Many of my classmates claim that my belief in a knowable reality, science, and reason is merely a form of faith. So how can a person validate his own reason and senses? How can a person know that they are reliable means of knowing reality -- unless he uses them and thereby engages in circular reasoning? My classmates claim that God is the only way out of this puzzle: God checks our reasoning by verifying and opposing our various conclusions. How can I respond to their arguments effectively?