Most schools and workplaces utilize whitelists and blacklists to filter content. They block known gaming websites (like Steam, CrazyGames, or dedicated flash game portals) and keywords associated with gaming. However, Google Sites is a productivity tool. Blocking sites.google.com would prevent students and employees from accessing legitimate educational resources, presentations, and group projects.
Most versions found on Google Sites are browser-based Flash or HTML5 ports. Classroom 6x - The Binding of Isaac: Wrath of the Lamb the binding of isaac unblocked google sites