Jon Star is an educational psychologist who studies children’s learning of mathematics in middle and high school, particularly algebra. Star’s current research explores the development of flexibility in mathematical problem solving, with flexibility defined as knowledge of multiple strategies for solving mathematics problems and the ability to adaptively choose among known strategies on a particular problem. Star also investigates instructional and curricular interventions that may promote the development of mathematical understanding. Star’s most recent work is supported by grants from the Institute for Education Sciences at the US Department of Education. In addition, Star is interested in the preservice preparation of middle and secondary mathematics teachers. Prior to his graduate studies, Star spent six years teaching middle and high school mathematics.