From a system theoretically grounded point of view, a hierarchy of primary and secondary impact factors influencing the mathematics teacher's choice to use practical activities in mathematics teaching is suggested initially in the article. A study, based on qualitative responses from mathematics teachers, then gives grounds for suggesting that a hierarchy of impact factors regarding the choice to use a practical activity in mathematics teaching must include more than just a binary clustering of primary and secondary impact factors. The teacher's everyday life experience, knowledge of pupils' everyday life experience, and the teacher's conscience are suggested examples of impact factors that might call for the introduction of a new level, as they are primary impact factors that seem to depend on adaptation to responses at the secondary impact factor level. This coincides with demands for strengthening of mathematical literacy in school mathematics and more independence for the teacher when it comes to teaching of mathematics.