I analyse low and high achieving children's competences regarding pattern and structure at the beginning of formal schooling comparatively. The aim is to evaluate the range of school starters' early structure sense. The results suggest overall high pre-instructional competences which, however, differ strongly between the mathematical high and low achievers. I name cognitive milestones for the development of a sound early structure sense. [This document was originally published as Lüken, M. M. (2011). School starters' early structure sense. Proceedings of the 35th Conference of the International Group for the Psychology of Mathematics Education (Vol. 3, p. 153-160).]