School buildings typically serve a number of functions simultaneously, owing to which they seem to be especially exposed to the expansion of fungi with wide enzymatic capabilities, including fungi of the genus Penicillium. In total, 34 isolates belonging to 20 species were obtained within two schools. The most frequently isolated species included: Penicillium chrysogenum, P. waksmanii, and P. citrinum. Over 65% more fungi were isolated in the heating season than when the heating was off. This period was also characterized by an almost threefold greater taxonomic spectrum. Especially in the heating season, the prevalence and species spectrum of the fungi of the Penicillium genus in school buildings should be constantly monitored due to their environmental plasticity as well as toxigenic, allergenic and antibiotic properties.