I too have recieved the dreaded letter... "your child will be expelled if the biting continues!"
Rest Assured your child is not a monster... they may just need closer supervision until they grow/mature a bit more. Biting is very common in the toddler years. (Or so I've been told by our Ped. and numerous Early Childhood Teachers)
My daughter is in a learning center/daycare. At around 18 months old she started biting other kids in her class (1-2 year old class). And it occasionaly still happens... We do NOT have the problem at home but we also do not have any other children at home for her to compete with.
TALK TO THE PRIMARY CAREGIVER IMMEDIATELY! You need their input on the situation (why is the child biting). Ask these questions... Is my child being properly supervised AND RECEIVING PERSONAL INTERACTION FROM THE CAREGIVER (NO CHILD SHOULD BE BEING HELD DOWN AND BULLIED, NOT EVEN FOR A MINUTE), Is your child sleeping enough, is he/she tired when the biting occures? Is your child hungry? Is the classroom over crowded? Are there enough stimulating toys in the room? Is your child teething? Has your child's schedule (or home environment) changed? Is your child's development in line with that of the other children in the class? How is your child being disiplined for biting? (never bite back, put hot/icky tasting stuff in mouth, I feel separating the child from normal activity is also not good) REMIND YOUR CHILD AT DROP OFF EVER DAY NOT TO BITE IT HURTS IN A FIRM VOICE. IF YOUR CHILD DOES BITE THE CAREGIVER SHOULD QUICKLY ATTEND TO THE BITEN CHILD AND SHOW YOUR CHILD THAT IT HURTS, ITS NOT NICE, SHOW THEM THE MARK, GIVE THE BITER TIME OUT FOR A MINUTE OR 2. AFTER TIME OUT HAVE THE BITER SAY SORRY TO THE CHILD THEY BIT.
After weeks of closer supervision and weekly talks with my Daughter's teacher... we feel that my Daughter bits more when she comes in late (days dad takes her to daycare). And that she interacts better with the older children in the 2-3 year old class (She has an more extensive vocab. compared to other kids in her age group) They have observed her telling other kids NO or MOVE and only attempts to bite after they don't listen to her. She also has no problems with bitting when she "visits" the infant room, and is actually very nurturing toward the babies.
KEEP IN MIND THE BITER FACES GREATER HEALTH CONCERNS OVER BITING. AND YOUR CAREGIVER CAN NOT TELL YOU ABOUT ANY HEALTH ISSUES OF THE CHILD YOUR CHILD HAD BITTEN. (as I've been told by our ped)