Send them away to be raised by someone else! It sounds intense, but during the medieval and Renaissance period in England, it was quite common for families to send their children to live with a different family to be taught things like a trade, but also how to behave. For most people, children were sent away in their early teens, to become apprentices and learn a trade. But for the aristocracy, the children were sent away much younger and in turn, their families also took in children from other families. The thinking was that parents loved their children too much to be properly strict with them. It was also believed that children would obey strangers more than their own parents.
A lot of aristocratic children were especially sent to the households of richer relatives or patrons. There, they would act as pages or ladies in waiting. This was especially done to teach the children how to behave at court and all the very fancy court manners (especially if their parents were not wealthy or noble enough to be part of the court themselves). These placements would also help the child to gain a helpful sponsor who was better placed to find them a good position or make a good marriage than the parents themselves. In turn, the children basically acted as servants (remember, ladies and gentlemen in waiting to the Queen and King actually WERE the servants because actual servants were too lowly to serve the Queen and King directly.)
Boys of course, were also prepared to be knights by passing through the stages of page and then squire. Combat training was a big part of their life away from home. Then, of course, as a squire, a medieval boy would be with the knight he served.
Catherine Howard, King Henry VIII’s fifth wife, was raised in the household of her step-grandmother, the Dowager Duchess of Norfolk, who was much more powerful and influential that her own parents. As a influential duchess, a whole gaggle of girls and boys were sent to live in her household and learn from her. However, the Dowager Duchess was somewhat lax in the supervision of these girls and boys and Catherine Howard had some early romances with the boys in the household which later helped convince the King to chop off her head. However, it was her connection to her uncle, the Duke of Norfolk (a powerful member of court) who got her placed in the Court to be noticed by Henry in the first place. So, you win some, you lose some in this system.