Unfortunately, the way this particular zip file was assembled, the file to load the entire scene is not within a Poser folder.  Look for a Schooltheater.pz3 file within that runtime folder; that file will load the entire scene.  Technically, the pz3 file should have been placed into the Scene Category of the Poser Library, but this set is old and created for an earlier Poser version.

Consult the readme documentation for further information.