What are the best grad schools that specialize in forensic archaeology?
University of Florida has an excellent forensic anthropology program. Dr William Maples who wrote Dead Men Do Tell Tales was the director of the department when my cousin studied for his doctorate in forensic anthropology.
There are two different fields, and from the question it is not clear which one your friend is interested in. Forensic anthropology studies (relatively) recently deceased people in order to solve crimes. Some physical or biological anthropologists (interchangeable terms) are bioarchaeologists and study long dead people (mostly skeletal remains) from archaeological sites. I don’t have any rankings for either case and most anthropology rankings were last done in the mid-90s and won’t be revised for another year or more. I highly recommend talking to actual people in your chosen field to get a sense of the requirements, time to degree, chance of working in the field, type of degree required for what you want to do (MA or PhD), etc.