How many children live on the island of Alcatraz not including Moose and Natalie?

There were 12 children living on Alcatraz Island, not including Moose and Natalie, as depicted in the book "Al Capone Does My Shirts" by Gennifer Choldenko. The story is set during the 1930s when the island served as a federal prison, and the children are part of the small community that existed there.