Wonderful post Peldon, latchkey children do consume library space and materials which could have been useful to others, but at the same time some children who are more interested in learning new things may also take benefit of that time to learn new things! However, I fully agree that no matter what, kids should not be left unattended in library, as librarians are not the one to look after them. And, parents/guardians should also be equally responsible and attentive towards their offspring.
Cheers!