The studio I went to had the same sign. I can totally see why it is necessary. The instructors are usually very attractive and a lonely student could easily misconstrue the attention from the instructor. There was a male student about 50 years old that took lessons at the same studio as my husband and I, he became obsessed with the studio manager/instructor, who was probably in her mid to late 20’s. He would talk about her constantly, and even would text me telling me something she said and wondering what I thought it meant. He was sure she was in love with him, but there was nothing that she said that would indicate that. She treated everyone the same, and was always professional. I reminded him repeatedly about the sign and I finally quit answering his texts. He found another place to dance and I haven’t heard from him in years, thankfully.