What to do if my 19 year old autistic daughter suffered bruises at the hands of staff at a residential school?

You could sue the school for negligence.  Negligence is the failure to exercise due care (that degree of care that a reasonable school would have exercised under the same or similar circumstances to prevent foreseeable harm).  An employer is liable for the negligence of an employee which occurred during the course and scope of employment.

Prior to filing a lawsuit for negligence against the school, it may be possible to settle the case with the school's insurance carrier.  Your daughter's personal injury claim filed with the school's insurance carrier should include medical bills and medical reports.  Compensation for the medical bills is straight reimbursement.  The medical reports will document the nature and extent of her injuries and will be used to determine compensation for pain and suffering, which is an amount in addition to the medical bills.  If the case is settled with the insurance carrier, NO lawsuit for negligence is filed.  If you are dissatisfied with settlement offers from the insurance carrier, reject the settlement offers and file a lawsuit for negligence on behalf of your daughter against the school.  You will need to be appointed guardian ad litem to file a lawsuit on behalf of your daughter.  If the case is NOT settled with the insurance carrier, you will need to file the lawsuit prior to the expiration of the applicable statute of limitations or your daughter will lose her rights forever in the matter.

If you can prove that the bruises were intentionally inflicted, you could sue the staff members for assault and battery.  Assault is intentionally placing one in reasonable apprehension of an immediate battery without consent or legal privilege.  Battery is the harmful and offensive touching of the person of another without consent or legal privilege.  It may be difficult to prove that the bruises were intentionally inflicted by the staff members instead of just other children at the facility.  Therefore, it would be advisable to pursue the negligence claim mentioned above instead of the claims for assault and battery.  Also, since assault and battery are intentional acts, the school (employer) could claim it is not liable because an employer is not liable for intentional acts of an employee since those intentional acts are deemed to be outside the course and scope of employment.  An employer is liable for acts committed by an employee that are within the course and scope of employment, which is why a negligence claim in your daughter's case would be easier to prove and where the school as the employer would be liable.