Resumen
The aim of this article is to compare three subject didactic measuring instruments (the SOM, LEMOSS(II) and LCH questionnaires) with regard to validity. These questionnaires are diagnostic measuring instruments, which teachers can use as an aid in certain didactic situations within the classroom. This includes the specialist planning of a specific learning opportunity, and as point of departure for the discussion of a learner?s learning competency in order to master specific and critical outcomes. High Pearson correlations between the different fields of the three measuring instruments, as well as between the measuring instruments as a whole, were found for grade nine learners in the Tzaneen and Phalaborwa areas. None of the questionnaires can be used as autonomous predictors of respective subject marks. However, the SOM, LEMOSS(II) and LCH questionnaires are diagnostic measuring instruments and therefore it is not of such critical importance for these questionnaires to be extremely accurate predictors of subject marks.