The purpose of our research was to check in what way (directly and indirectly) and to what extent the natural science items in the 2015 PISA research, are connected with the objectives determined in the primary school curriculum. We went through the objectives of seven different natural sciences curriculums and studied 277 questions from the field of natural sciences. We put the objectives into two groups – practical and contextual, and determined that contextual objectives are prevalent in all of the curriculums. We also checked how successful our students were at solving the natural science exercises. The students’ achievements were analysed based on seven characteristics of the exercises – the field of study, the theme, scientific competences, the type of knowledge needed, the cognitive level of difficulty, the type of question, and the number of objectives from the primary school curriculum. With our research, we determined that most connections between the questions and the objectives are circumstantial (64,3 %), and only a small percent of them (35,7 %) are directly connected. When analysing the students’ achievements based on the characteristic of the exercises, we determined that the field of study, the theme and the number of objectives from the curriculum connected with the question, have no influence on the result. It can be deduced that the students have a similar level of knowledge of all the fields and themes from natural sciences. Distinctive differences were determined with three exercise characteristics: the types of knowledge (contextual, procedural, epistemological), the types of questions (open, simple multiple-choice, complex multiple-choice), and cognitive difficulty (low, medium, high). The students had worse results at questions that were testing epistemological knowledge, those that were open-type, and those of medium and high cognitive difficulty.