I am aware of considerable concern about the possible detrimental effect on children of carrying heavy school bags. My own view is that optimum solutions to this problem are most likely to be achieved at school level.
Teachers and parents working in partnership at the level of each individual school can make suitable practical arrangements for schoolwork and homework. These involve time-tabling and advance planning by teachers so that pupils know in advance what books are required on any particular day. Arrangements for storing books in schools where this is possible can also be helpful.
Parents can ensure that schoolbags themselves do not add to the problem by being excessively heavy and also by ensuring that pupils do not carry unnecessary material in their schoolbags.