Although ammeters are very important tools for science classes in elementary and junior high schools, many ordinary ones are not easy to handle nor sufficiently educational. From this viewpoint, the authors have investigated the possibility of using clamp-on ammeters, which are very common among professional electricians, for educational purposes. It has been found that clamp-on ammeters are useful in science classes in junior high school and that many students felt them easy to use. In particular, our ammeters are expected to be very effective in reducing the time students spend on experiments because it is not necessary to rebuild the circuit to connect the ammeter before measuring the current. (Contains 3 figures and 5 tables.) [Appended to this document is: "Appendix 1: Questionnaires in the First Investigation"; and "Appendix 2: Questionnaires in the Second Investigation."]