Naturally radioactive sources were developed using three easily available and familiar substances: potassium chloride, instant coffee, and kelp. The radiation fields that they generated were actual measurements using various instruments to adapt the sources to school radiation education. It was quantitatively found that the potassium chloride source can be used for qualitative experiments on β-rays. The latest national Courses of Study published by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) have been applied since 2020. By the results of our measurements with the Courses of Study, an example of experimental training using naturally radioactive sources: “Absorption training Experiment of β-rays Using Shielding Materials” was developed. We believe that the widespread application of naturally radioactive sources made of familiar materials will make it easier for schoolteachers to carry out radiation experiments in their classes and contribute to establishing the publicʼs literacy on radiation.