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Filius.
Professor Filius Flitwick was a former duelling champion.
Professor Filius Flitwick teaches Charms at Hogwarts School of Witchcraft and Wizardry.
Flitwick is also the head of Ravenclaw house.
There is no 'Fillus Fitwick at Hogwart'. There is however Filius Flitwick at Hogwarts who is the Ravenclaw head of house.
It does not specify in the books