In The Goblet Of Fire we see that Madam Maxime and Karkaroff did not know details about the Tournament's tasks (it is best seen on the dragons example). Apparently it was done to avoid them helping their champions get ready for the tasks. The whole event is soaked with atmosphere of distrust and rivalry. How come then that they were OK with Dumbledore and at least some other teachers (Hagrid, Moody, McGonagall) from Hogwarts to be aware of the tasks and thus to be able potentially expose the details to their champions (especially after Hogwarts having two champions instead of one)?
Here is a quote that shows Moody already knew about the dragons.
Harry wondered what was in there, until Moody's next question brought him sharply back to earth. "So. . . found out about the dragons, have you?"
There is also a passage that makes me think McGonagall also new about dragons before the task:
He left the Great Hall with Professor McGonagall. She didn't seem herself either; in fact, she looked nearly as anxious as Hermione. As she walked him down the stone steps and out into the cold November afternoon, she put her hand on his shoulder. "Now, don't panic," she said, "just keep a cool head. . . . We've got wizards standing by to control the situation if it gets out of hand. . . . The main thing is just to do your best, and nobody will think any the worse of you. . . . Are you all right?"
And of course Dumbledore is supposed to know what is going on at the school grounds. So why would the Tournament rules prevent the heads of other schools know it as well? Does not seem fair at all.