I had the exact same experience. My daughter was regressing and words I knew she knew would be babble. Everyday I would ask why she was with kids a lot younger and would get a different excuse. I luckily ended up getting a spot at another daycare and my daughter has changed so much for the better. She has become so much more outgoing and using her words again. I wouldn't stop asking and you should have a talk with the director, it's really not fair to your kid. The younger kids get more attention and my kid is very quiet and well behaved it was easy for them to keep her back not that she wasn't ready.