Grunkemeyer grew up in
Lewis Center, Ohio, and started playing several sports from a young age, including
flag football starting at three. He attended
Olentangy High School where he played
football and
basketball, being a
quarterback in football. He was backup quarterback as a
freshman and then became starter as a
sophomore in 2021, throwing for 2,152 yards, 16
touchdowns and 10
interceptions. He then threw for 2,649 yards and 25 touchdowns as a
junior. In his
senior year, Grunkemeyer helped Olentangy compile a record of 11–2 while throwing for 3,517 yards and 39 touchdowns, being chosen first-team all-state. He was also named first-team all-conference, first-team all-district, the conference co-offensive player of the year and the county offensive player of the year. He finished as the Olentangy career record-holder for both passing yards and passing touchdowns, while he also set single-season records at Olentangy in those categories. Grunkemeyer was initially lightly recruited, having no
offers as he started his junior year and only one (
Miami of Ohio) by the end of it. He committed to play
college football for the
Penn State Nittany Lions. ==College career==