It should be. It has the same effect on people - they grow too much too fast, but remain immature and fragile both mentally and physically. They do hit puberty very early though.
do you have any reference to that claim that Pb is positively correlated with growth/height, either in crops or in people?
Did you just requested "supplementing" children and adolescents with lead?
Looks like you had too much of it yourself :)