Social studies and history teachers should be free to expose students to controversial ideas and to teach critical thinking skills. But are they free? Do they have the constitutional right--call it academic freedom--to teach what they want and to discuss controversial issues in the classroom? The short answer is "no." In this article, the author warns that teachers should not presume that their legal rights are protected by the First Amendment rather than by legally enforceable teacher contracts. He suggests some actions teachers can take to insure that their classroom remains a marketplace of ideas. (Contains 35 notes.)