Understanding how struggling students approach math is vital to designing effective math lessons. Many low achieving students rely on a weak knowledge of procedures and attempt calculations without adequate consideration of the problem. We investigated how enabling or preventing premature calculations affected learning math. Students were presented with explanations of math problems that either contained numbers, thus allowing for calculations, or contained variables, thus preventing the possibility of calculations. In Experiment 1, we asked students to learn from a conceptual explanation and found that preventing calculations was beneficial, especially for students with less prior experience in math. In Experiment 2, when the lesson was procedures-focused, we found that preventing calculations did not have the same beneficial effect. Students with less prior experience performed poorly compared to those with more experience. Given students' prior math experience and their usual approach to problem-solving, we can facilitate learning by blocking maladaptive approaches.