This study aims at investigating the effect of grade level on students' achievement in matter concept and reasoning abilities, when their test anxiety was controlled. The data was collected from 8th, 10th and 11th grade students by the administration of The Matter Concept Test, Test of Logical Thinking, and the Motivated Strategies for Learning Questionnaire. The results revealed that there was a significant effect of grade level on students' achievement in favor of 11th grade students and the linear combination of reasoning abilities was significantly related to students' achievement. In the Matter Concept Test, the 10th graders did better than 8th graders and the 11th graders did better than either. The only exception to this general observation was the 8th graders' better performance on a small number of questions, which related to topics that were taught and nationally examined in the 8th grade. It seems likely, therefore, that the more chemistry a student is taught the better he/she is likely to be, except that if a topic is examined while it is reasonably fresh in a student's mind the results are likely to be better than if the test is carried out 2-3 years later. © The Royal Society of Chemistry.