This is what it said the Yeerks did with children (of any species) in book #41
"The Yeerks raise children in large warehouses back in the city. Controllers like the ones you saw are picked at random to procreate. When children are born, they enter one of the wamps, or warehouses, where they are held from birth to age fifteen.
Their lives are controlled though their brains are left uninfested. Children are seen as weak and unworthy host bodies.
"During this captivity," she continued, ; "they're pumped full of vitamin supplements so the host bodies will grow strong. They're run on
treadmills so they'll be fit to fight and to produce. When instinct leads them to indulge in moments of uncontrolled, regular childhood, they are punished.
If they try to educate themselves, they are punished. Yeerks want minds as powerless as possible. So they raise children in a joyless, lifeless world where they wait for the day of infestation.