Newtonian mechanics is still among the most difficult topics in the physics' syllabus taught at school. For example, even after completing traditional instruction, students still think that a force is necessary to maintain motion. Therefore, a revised method of instruction is needed that meets students' learning needs. The aim of the project presented in this article was to develop and evaluate novel teaching units for the introduction to Newtonian mechanics. Rather than changing methodology, the content area itself was restructured innovatively with careful consideration of the most common preconceptions. Based on diSessa's notion of conceptual change as the reorganisation of these only loosely connected preconceptions, so-called p-prims (diSessa, 1993, 2008), the strategy pursued was aimed at triggering the activation of appropriate p-prims while avoiding the activation of inappropriate p-prims. For example, to lower the activation priority of the above mentioned notion, a consistent introduction to mechanics via two-dimensional dynamics was chosen. In the first year of the corresponding study, 10 participating teachers taught their 7th-grade classes in the traditional one-dimensional way. In the following year, the same teachers taught (other) 7th-grade classes using the revised twodimensional way. Students' knowledge of mechanics, self-concept and interest in physics were assessed. This quasiexperimental field study showed a significant improvement in students' conceptual understanding. Thus the findings of this project suggest that altering the content structure of a particular topic might be an important parameter to improving learning outcomes.