Schools do not teach any critical thinking and for good reason. Ivan Illich wrote "Deschooling Society" in the 70s and John Taylor Gatto started writing the "The Underground History of American Education" in the 90s. Either should give you insight into why teachers do what they do, but Gattos's "Weapons of Mass Instruction" is probably the best place to start. The short answer is that schools are designed from the top down to stunt the intellectual growth of children regardless of the intentions of teachers.