the youth strength training guideline established by the national strength and conditioning association recommends one to 3 sets of 6 to 15 repetitions for 9 to 12 years of strength training. each with appropriate weight load.
what is an appropriate weight?
in adults, some tests can be used like 1 repetition maximum (1RM) or even (10 RM) that represents the 100% of the participants then we can set the appropriate intensity according to the 100%.
in case of children strength training what stands for these measures?