Citizen science (CS) is considered a powerful supplement for teaching natural sciences (and beyond) at school. Even though involving children of primary school age in scientific activities is still uncommon, previous studies confirmed that they can contribute meaningful data as citizen scientists. Yet, the administrative efforts of organising the pupils‘ participation in research activities are high for both, schools and scientists. Typically, some children benefit enormously from participating in a CS project; however, others don’t. To enable decisions for school representatives and funding agencies, empirical tests of the learning benefits of involving CS in routine teaching are needed. This chapter focuses on CS in the education context and wraps up the results of critical tests of (i) factual learning during a project on the social behaviour of a free-living bird species, that is, Greylag geese (Anser anser), (ii) conceptual learning, that is, the transfer of knowledge to new contexts and the children’s concepts of ‘friendship’ and (iii) impulsive behaviour control in primary school children involved in a project as citizen scientists.