In his excellent series The Impressionists, critic and art historian Waldemar Januszczak discusses at some length the stunning and innovative ballet studies of Edgar Degas. But he left out a major aspect of his work, which is surprising given how thorough his research seems to have been overall. Appearing in some of Degas's paintings are dark shadowy figures watching the "ballet rats" as the students were often referred to, with some interest.
These "patrons" were welcomed by the ballet schools as they were an important source of income. But it is well documented that rooms were set aside at the rear of these schools for "extra curricular activities". Many mothers sent their daughters along to these schools knowing this was happening and because it was happening, in the hope their daughters could bring home some cash that might keep the rest of the family alive. This is the 19th Century and poverty was endemic in inner Paris.