Critical and higher order thinking is essential to education, but it is not clear what teachers understand this to mean and what role this has in their instruction. We interviewed 38 teachers in Kindergarten to Grade 9 classrooms from 14 schools in Newfoundland and Labrador, Canada, to obtain their understandings of critical and higher order thinking in social studies and science, and how this affects instruction and assessment. The teachers believed that higher order thinking was important for all students, and attempted to teach thinking; however, they were less sure of how they might assess thinking. The teachers indicated uncertainty about what higher order thinking means, and believed they were not well prepared to teach or assess higher order thinking.