Teaching for understanding requires teachers to organize thought-demanding activities which continually challenge students to apply and extend their prior knowledge. Research shows that student teachers often are unable to develop lessons in teaching for understanding. We explored how a domain-specific heuristic can assist student biology teachers in developing problem-posing lessons according to teaching for understanding. Worksheets of lesson plans were analyzed according to criteria for problem-posing lessons. Furthermore, student teachers' perceptions of the design heuristic's usefulness were categorized in a cyclical process. In general, the heuristic appeared helpful to most student teachers for designing problem-posing lessons satisfactory according to the criteria. Furthermore, teachers indicated that using the heuristic deepened their subject matter knowledge and their awareness of pupils' prior knowledge.