...Never had a teacher in any of my public education days use a circle to mark an answer wrong... It was always an "X" But, yeah, using check marks to signify a wrong answer is just... damn odd.
Always hated the "mark every answer right or wrong" method myself since it ends up making the paper full of red marks regardless of whether you scored well or not. If there's nothing next to it, it's just logical to assume it's correct to begin with.