Abstract
Diagnostics of a pupil's abilities and skills is an important element in formative assessment in (not only) mathematics education. Formative assessment currently sets the trends in increasing effectiveness of education.
The paper describes a diagnostic method that was implemented using data from a research project where the so-called column tasks were set to pupils of the 2nd grade of primary school and then used as a diagnostic tool. The tasks are characterized, their gradation parameters and their diagnostic potential are presented.
For each of the 10 tasks the mistakes that appeared in the pupils' solutions are presented. In case of the most common mistakes, we look for their probable causes and propose reeducational procedures. We use one specific case to show how some re-educational procedures can be formulated for a specific pupil.