Someone who judges another person in a very strict, inflexible way can be described as Rhadamanthine. It can be a little intimidating to have a teacher who is well known for their Rhadamanthine enforcement of rules.
The word Rhadamanthine derives from Greek mythology — Rhadamanthys was a demigod son of Zeus who became one of the three judges of the underworld. Anyone whose judgments are especially stern and rigid is Rhadamanthine, and the word is sometimes used by legal scholars to describe judges who interpret law in an extremely literal and inflexible way.