Ministers want to add a fifth dimension to the classifications of schools under HMI inspections.
Peter Peacock, Education Minister, believes that the present four categories - unsatisfactory, fair, good and very good - do not do justice to the "truly excellent school".
"We want to make every school truly excellent. It's about raising the standard for all. For most kids in Scotland there is no choice about where they can go to school," Mr Peacock said. "That is why, if for no other reason, we have got to make sure that every school is excellent because a lot of pupils have no choice."
Schools deemed to be excellent are unlikely to be reinspected for a number of years under the new inspection regime.