Continuity mistake: When Max goes to talk to Miss Cross after the initial opening of the Aquarium, she is sitting in a playhouse with several little kids around her. Max approaches and ducks under the low roof so he could sit down and talk, but somehow all the kids around Miss Cross have disappeared.
Continuity mistake: After Miss Cross resigns, she is shown packing her things in her classroom. She removes the middle one of three children's paintings on a board. When the camera shows the board a few seconds later, the top two paintings remain and the bottom one has been removed.