I have a 4 year old girl who used to be just the sweetest, most polite little girl I''ve ever met. Over the past 4 months her behaviour has become more and more rude and aggressive. She's sneaky, and only does these things when she thinks my back is turned. Laately I've been exhausted just trying to deal with her. The other children are losing the attention they deserve and I can't turn my back for a minute without someone being tortured in some way by this child.

I talked to the parents about cracking down on her. They said they were at home too. Time outs, sitting out, having toys and privileges taken away does not work. She just becomes more angry (that she got caught probably) and works harder at finding small sneaky ways to drive her friends insane.

Todayt a parent showed me a bit mark upon arrival. The child she did it to is quiet and does not cry so I had no idea. She bit this little boy HARD enough to leave a mark that was still quite visible this morning. Later this morning I caught her holding a two year old by the arms (hard) and shoving her face i nto the child, then she's stepping on the back of everyone's heels outside (she's wearing shoes and they are all in sandals)

I put her on a sticker program yesterday. She has ZERO interest in it no matter how I hype it up

I'm at a loss

I'm not sure what to do anymore. This family has two kids in my care that makes up 40% of my income. But, i can't continue on like this much longer.
How long do you guys think should give before I call it quits? Any new suggestions?