I'm not convinced that yours is the only literal way to read it. The question of who exactly is doing the "leaving behind" is implicit, but it always sounded to me like it was the adults, not the other children. I don't think it's any less literal to interpret it as making sure some adults linger behind with the children who are behind rather than all of them running ahead with the children who go faster. The phrase isn't "no children are behind", which would be the literal representation of what you're saying; "left behind" is a bit ambiguous, and while I think you can make the case that the ambiguity is a problem, I don't think it's nearly as clear-cut as you're saying that there's only one literal way to read it.
