a biter among us

I know that this is a stage that alot of babies go thru, but Seth was bitten 3 times last week at daycare! Seth has never bitten yet, but i'm scared he is going to pick it up from the biter! Daycare cannot say who the Perp is, but I have a pretty good idea who it is. Seth is the only boy amongst 3 other girls at daycare and 1 of the girls is particularly feisty! Daycare doesn't seem to worried about it and they always tell me "well...Seth did take a toy from her". Don't all babies take toys from each other? I don't think sharing is a concept that they really understand until about age 3. They all take toys from each other, but they make it sound like because he did this then it's okay that she bit him. Well it's not and him coming home with bite marks almost every day is not okay with us! I have been looking into other daycares but everything is soooooo expensive. Ours is the cheapest in the area. I guess you have to pay for quality! Okay, I'm done with my venting now!