Actually, they (the Pearls) tell a story about a little girl spanking her dollies for having a bad attitude and raved about what a great mother she was going to be.
Apparently, that's the defining element of good mothering.
They do allow older children to spank younger ones, and if kids hit other kids who are their same age (without approval in other words) they would be disciplined for that. So the kids would learn which people they are allowed to hit and which ones they're not... preparing them early on to accept and endorse the double standard of punitive Christian "discipline."