A professional core includes a common language of practice, foundation principles and skills, and related standards. Such a core is present in the medical, engineering, and legal professions. Instructionally, it is not present in the teaching profession. There is no core foundation for critical instruction. Such instruction, long sought but unrealized, leads students to think, read, and write critically for content comprehension. These issues obstruct critical instruction:There is no uniform use of instructional terms.Conventional serialism-based instruction blocks the mind’s nature to think critically. Rote learning is the result.Teaching is based on thinking directed at subject matter. Yet, we practice without a universal foundation in either.Teacher preparation programs have no foundation courses for critical instruction.There are no teacher-educator, teacher, or student standards for critical thinking for comprehension, the basis of critical reading and writing.These issues result in weak instructional preparation and practice and poor student achievement. Fixing Instruction resolves the issues. It provides, for the first time, teacher-educators, teacher-candidates, teachers, and professional developers with an explicit core body of knowledge for critical instruction.