Cultivation of microorganisms such as fungi and bacteria is often not included in scientific inquiries conducted in school because of the difficulty of manufacturing a suitable medium. A method using dry rehydratable film to reduce the need to manufacture a suitable medium and shorten incubation time was developed as an efficient microbial testing method. Using this method, students can easily perform experiments on microorganisms in schools where time and space are limited. For example, we carried out an inquiry on the possibility of drinking refrigerated milk that is already past its expiration date. Through this activity, we could raise issues related to the current shelf-life labeling system implemented in Korea. In addition, the method can measure microorganisms in several ways through air, direct contact, and indirect contact, making the procedure easier to use in scientific activities at school.