Lesson planning is a challenge for teachers. However, the measurement and modelling of teachers' competence to plan lessons has received little attention. Especially, the question of which aspects are of central importance remains largely unresolved. The study aims to measure the challenge of structuring a lesson as an aspect of the situation-specific ability of lesson planning competence. To this end, we developed a standardised method for analysing written plans of demonstration lessons during induction. Using appropriate indicators, the situation-specific planning perception, interpretation, and decision-making of pre-service teachers is reconstructed. The sample consisted of 211 written lesson plans of 106 pre-service teachers from the "PlanvoLL project." The lesson plans were evaluated through content analysis. The generated codings were then quantified and analysed with Item-Response-Theory (IRT) scaling. Results show that structuring can be reliably measured. Measurements of perceived competence increased during induction. This study contributes to the development of a meaningful empirical model of how the process of lesson structuring can be measured as a competence construct and to research on the measurement of planning competence among pre-service teachers.