Abstract
The establishment of single sex classes in mixed secondary schools has been proposed as a strategy to increase the participation and achievement of girls in physics. This paper reports some findings from a three-year longitudinal case study of two single sex GCSE physics classes in a mixed comprehensive school in England. The results indicate that girls who elected to study physics in a single sex class gain confidence in the subject over the GCSE course, that gain in confidence is associated with better GCSE achievement, and that this increases the likelihood of studying A-level physics.