The purpose of this study was to establish what impact experimental work has on the understanding of scientific concepts, what pupils remember about the experiments they carried out and how they are able to formulate and understand the experiment plan. A sample of 386 pupils aged 13+ participated in the research, of which 162 in the experimental group conducted 5 experimental science activities. Instruments used with all pupils in this study include: pre-test, knowledge test, delayed knowledge test and questionnaire, while 39 of the pupils also took part in semi-structured interviews. The results show that 35.8 % of pupils in the experimental group failed to write down at least one experiment they remembered from science classes, and none of remaining 64.2 % of pupils that wrote down at least one experiment correctly described it. In addition, the results of the interviews show that only 2 pupils remembered the experiments from 5 experimental science activities three months after the experimenting without interviewer's help, and only 5 pupils were able to adequately name and describe those experiments and interpret the experiments' findings. Although they were unable to describe the experiments, the students in the experimental group scored higher on the test and the delayed test than the pupils in the control group with a statistically significant difference. The results of the survey also show that pupils believe experiments to be the most popular part of science classes. (Contains 3 figures.)