The Oakland native graduated from DBP in 2004 and went on to become a star quarterback at Rutgers.
In 2015, he was hired by former coach Greg Toal as the Ironmen's new offensive coordinator for the Ironmen, before taking on his new role in February 2017 when Toal was dismissed from the team.
"Don Bosco Prep was the foundation that my education and athletic career was [built upon]," he wrote on Twitter.
"This school has been, and forever will be, a very special place to my family and I. I've created lasting memories here as a player and coming back to coach has been incredibly rewarding. That's what makes this day difficult for me.
"I have been considering professional business aspirations outside of the coaching profession and ultimately have decided that a change in career path is the best decision for me right now."
In his first season with DPB, the Ironmen finished 2-8 (they're lowest since 1994). Last year, the team finished 6-5 before falling to Bergen Catholic in the Non-Public Group 4 semifinals 35-17.
"I want to make sure that the program is positioned to succeed both short- and long-term and stepping away right now will allow us to find the long-term successor," said Teel on Twitter. "I will continue to be a champion for the program and act as a resource anyway I can to ensure we reach our goals."
Click here to follow Daily Voice Northern Valley and receive free news updates.