Tips/Tricks That Have Worked

Hello all! My question is a semi-normal occurrence from what I've seen, but none have touched on things that have worked.

I have a 17-month old son. He is in daycare fulltime and has starting to pickup up the habits that he has seen from other children, the daycare lady's own child to be more specific.  She does not discipline the children when stuff is occurring. Her child has autistic characteristics and a sensory problem. Therefore, thrashing himself on the floor in a tantrum, hair-pulling, biting, hitting, and ear-piercing screaming is the norms for him. Unfortunately this has become impressionable onto my son. Mind you my son has no issues but he now mimics the child with known causes.

At home, my son will do these same things and no discipline whatsoever seems to work as he laughs and does it again. Each time we reiterate "no _____, it hurts", we've tried timeouts, set in his room in his crib with nothing, but at 17-months old he doesn't seem to care what he has and doesn't have and nothing is working.

Is this the time we leave and go to a new daycare? I'm sure though there will be another who he'll mimic and then back to square one. So I'm trying to cut the actions themselves however, everything I've read to-do, we've already been doing. Does anyone have a sure-fire break? Something out of the ordinary that's helped them?

Thanks in advance!