Like years of AP Physics C classes before them, when this year’s crop of Phys C students stepped into their first class today, they were greeted by physics teacher John Feulner in his “I <3 Physics” T-shirt.

His astronomy students received a similar welcome. For them, Feulner changed midway through the day into an “I <3 Astronomy” T-shirt.

Sure, science teacher Walt Werner occasionally wears a biology T-shirt, and science teacher Blaise Eitner dons a rhinoceros T-shirt every day one of his classes takes a test, but no one tops Feulner, who wears a science-themed T-shirt every day of the school year.

“I’m either in a science T-shirt and my athletic pants, or a suit and tie when I go to board meetings,” Feulner said. “I don’t have anything in between.”

Every August, Feulner throws his heap of T-shirts onto his bed to organize them for the coming year, so he can wear the relevant T-shirt for each lesson.

“The more I got, the more I realized I really needed to organize them because there are those occasional times when I don’t have a lot of time in the morning, and I can’t seem to find the one that I want,” Feulner said. “And if you pass it by—it’s gone.”

Feulner began wearing themed T-shirts as a college student. When he began teaching at Harvard School for Boys, he decided to search for shirts specific to his lessons. The more he bought, he said, the more he felt obligated to have a shirt for every day, even if that meant designing his own T-shirt when he couldn’t find a certain subject.

Although the common passerby might not be a fan of his black hole T-shirt that says “What happens in the event horizon stays in the event horizon,” Feulner said his students like them, and sometimes gift him their own.

“If you’re into black holes, then that’s funny,” he said. “If you’re not, then it’s probably just dumb.”