Teaching critical thinking in school can't stand up to the power of indoctrination by Mom, Dad, and God at home. Religious parents actively work to ensure that their children see them (and the church) as the only authoritative source of truth.
Way to paint with a broad brush. Catholic schools are full of the children of religious parents, and the instructors are usually priests and nuns. The nuns will kick your damned ass if you're intellectually lazy. Whenever I reflect on my education, I always thank Sister Catherine Joseph, one of my 6th grade teachers. She was a mean woman, and I hated her guts, but she was one of the best teachers I've ever known. She taught two subjects: Science and Religion, and she taught both of them rigorously, and well.
Never underestimate someone who believes they have been commanded by god to turn your child into a thinking, reasoning, well educated member of society.