The principles of pre-war didactics of science

The pre-war didactics of Science was directed by some important principles. This principles, were valid in elementary schools and were accepted generally. These rules were evident in old textbooks, methodical and didactical literature. One of the rules was rule about non-using Physics formulas. Exercises which were solved, were solved only by simple mathematic operations and word rules. Could this rule be interesting for today pupils or teachers?