That's just silly - children need to be fed and nurtured in order to maximize late life growth potential. I believe if you work children too hard as children it may not be optimal for their post pubescent growth. I don't think any medical studies have proved my claim though, which means that it's okay to use children as a source of labor
Heck if I'm wrong it would just make them stronger anyway.
But this goes against my view that humans and extinction is inevitable and thus if they died now it would make no difference except to those anthropocentric humans.