Spell classification levels as of 823 A.D. revised 1000 A.D.
S accidental magic and household charms
SS Transfiguration and weak combat magic (warning of pending expulsion sent)
SSS Mid-level combat magic (flame whip) and much of what is learned at hogwarts
SSSS High level combat magic and large scale transfiguration as well as standard wards( Aurors sent for everything over)
SSSSS Blood magic (highly illegal) (hit wizard squad sent)
SSSSSS Powerful wards such as blood wards
SSSSSSS Unforgivable level
SSSSSSSS Above unforgivable level ancient beings returning contact DOM ( Department Of Mysterys) and flee for you life