In this thesis are described student activities in computer science classes in primary and secondary schools. Activities, as a more contemporary learning process, enrich teaching methods and stimulate students' creativity. The most important outcome of introducing activities into class lies in the fact that children, by exploring, develop conceptual knowledge which results in enhanced long-term knowledge retention. The first chapter describes the benefits of introducing activities. In particular, two examples of good practice from around the world have been described, namely the American CSTA K.12 and the English national curriculum. In the case of the American national curriculum an example of activities from the respective document was presented, with no translation provided. In the following chapter concrete activities were listed which can be implemented in primary and, with a little refinement, secondary schools. The activities are divided in four parts: mathematical principles of computing, graphic representation of data and spreadsheets. The chapter Mathematical Principles of Computing outlines the activities by which the students discover the concepts of bit, variable and command execution in computing. The chapter entitled Algorithms focuses on the activities by which students discover the greatest element of a set, insertion sort and binary search. The chapter Graphic Representation of Data focuses on activities by which the students discover the bar, pie and line chart. The last chapter describes the activities by which the students discover discount percentage, average sprinters' times and monthly salary calculations in Excel. Beside providing a detailed description of activities, the paper also raises questions for discussion.