Mullen made his mark during 24 years at Central as an award-winning history teacher. After the OPS and UNO graduate joined Central in 1999, he showed dedication to both his profession and students. Particularly passionate about African-American history, he helped uncover lost history of Omaha’s minority communities as part of the OPS Making Invisible Histories Visible program. Before retiring in 2022, he was honored as Central’s teacher of the year (2019), with the Alice Buffett Outstanding Teacher Award (2020) and History Nebraska’s Excellence in Teaching Award (2022). “I know I’m not the smartest teacher, and I’m not the most gifted teacher, but I pride myself on being the hardest-working teacher,” he said.