A Fauntleroy suit with a kilt rather than knee pants could be worn by quite old boys. The classic Fauntleroy suit was a black or dark blue velvet suit with knee-length velvet trousers. Some mothers in the 1880s and the 1890s were enchanted with the Mrs. Benetts' Fauntleroy suit, but did not believe their boys, who were still wearing dresses, were quite ready to be breached . I have slowly been acquiring information in this topic. Young boys wore dresses throughout the 19th Century.
Dresses are one piece garments without separate jackets and skirts.
In many cases they were styles indistinguishable from their sisters with ruffles and lace. Many mothers might choose the plainer styles for their sons, but others preferred the same more elaborate styles worn by their daughters. In such matters it was up to the preference of the mother. Often if a boy had an older sister, he would wear her old dresses. Thus the Fauntleroy-style dresses were not great departure.