Heitmann is someone who respects duelists with high potential and strong monsters and despises duelists with low potential and low monsters. He tried to expel Leo, Luna, Dexter, Bob, Patty and Sly due to their low performances. Yusei duels the teacher to make sure that the students wouldn't get expelled. Heitmann lost the Duel to Yusei by the same low monsters he despised.
In the dub, the Principal reveals that Heitmann only maintains his high position because his mother (whom he still lives with) is one of the Academy's principal sponsors.
Heitmann uses a Deck based on "Ancient Gear". (In the dub, he calls it a "Vanguard Deck", but given his ego, he likely made that up.) According to him this is a vintage Deck that only Elite professors chosen by the Academy are allowed to use. Thus it is unknown if this is his real Deck or just a Deck used by all Head Instructors at the New Domino City Duel Academy.