1,125. The Age of Chinuch

165:2 The time to start teaching children positive commandments depends upon their individual levels of understanding. For example, one who understands about Shabbos is obligated to hear kiddush and havdalah and similar such things. Negative commandments, whether Biblical or rabbinic in origin, must be taught to every child upon reaching the age that he understands when told that a certain action or food is prohibited. One should teach children to respond "amen" and other responses in shul. A child has a place in the Next World from the time he responds "amen." They must be taught to behave properly in shul, otherwise it would be better not to bring them.

165:3 Even one who is not a child's parent is not allowed to give him a prohibited item to eat or to tell him to perform a prohibited act. According to most authorities, even something that is only prohibited rabbinically may not be given to the child to eat or be instructed for him to do. If the child is a little sick and needs to eat something prohibited, he may be given something that's prohibited rabbinically, by a non-Jew. Regarding giving the child chometz on Pesach, see the laws of Pesach.