I would suggest in a scenario like that, unless the teacher gave you a card for HER class, that the advice is well intentioned. Chances are that this particular teacher doesn't teach 3yr olds :-), it's a niche thing.
We had to work pretty hard to find a ballet class that would take my 2.5yr old (I caved after months of begging and hysterical tears every time her older sister went to HER ballet class). The place we found is actually really ideal for her in that they cater to 2-5yrs olds only, the teacher dresses up as "princess bows" (which keeps the smallest kids attention, the LOVE her) and she's really good at managing the children, all the children, from the terrified 2yr olds who don't want to be there are cry through the whole lesson, to the 5yr olds that can do everything and should be in proper classes. So my 2.5yr old was able to get instruction at her level (not much!) while not disrupting the class more than any other child by hanging upside down from the bar. She was the only one hanging upside down, but there were plenty of other kids doing other "wrong" stuff. A year in I have gotten over my horror that the class is taught by "princess bows" and I appreciate how much she manages a really emotionally, socially and physically diverse bunch of kids. My DD has made quite pronounced progress in that time too, in group participation AND ballet skills. She will be ready for pre-primary "real" ballet well before her older sister's teacher is usually willing to take kids and she will thrive when she transitions - but I SO don't think that my older daughter's wonderful RAD teacher would have been remotely the right person at 2.5yrs!
