The ability of TPE participants in arranging lesson plans is essential to be mastered as an indicator of pedagogical competence which should be possessed before conducting a teaching process in the class. This research aimed to analyze the estimation of TPE participants' ability in composing a lesson plan which uses the assessment with partial scoring. This research used quantitative descriptive explorative approach. Data were collected through document study of lesson plan made by TPE participants assessed by lecturers in a workshop. In the sample were 236 respondents selected by using purposive sampling technique. The data analysis was performed to estimate participants' skill using Item Response Theory through Partial Credit Model (PCM). The estimation result produced the interpretation of items with 5 categories of scoring 0, 1, 2, 3, 4 and has 4 thresholds such as the threshold of category 0 to category 1, category 1 to category 2, category 2 to category 3, and from category 3 to category 4. Besides that the information function value of the instrument and Standard Error of Measurement based on the analysis obtained items in the instrument which have higher information function value compared to the mistakes of the measurement or the estimation of measurement which has relatively small errors, so it can be stated that learning model is using accurate partial scoring to estimate the ability of TPE participants in composing lesson plans.