There is a rabbinic obligation to wait between meat and dairy though customs are diverse regarding how long to wait, ranging from 1 hour (for those who come from e.g. Dutch communities) to the more common 6 hrs. With regard to small children, the general custom is to gradually increase the amount of time they wait as they get older until they wait the full time that adults in their community wait. My question is: within, e.g. the communities that wait 5+ hrs, is there a standard protocol to follow across childhood? Are there any published (or oral) rabbinic rulings? Please cite the names of the works or authorities.
Rabbi Moshe Sternbuch in Teshuvos V'Hanhogos 1:435 says as follows. He says as soon as a kid has an understanding - even at the young age of two - they should start waiting the minimum of 1 hour which is the Shiur mentioned in the Rama Yoreh Deah 89. At the age of 5-6 when there is Chinuch L'Mitzvos they should start waiting 3 hours. At the age of 9-10 they should wait the full 6 hours.
He says the Chochmas Adam 40:13 is lenient with someone who is ill and that would be the case with a child that one can be lenient to some extent.