Patrick Arnold was named to All-Nebraska First Team for all classifications by the Omaha World-Herald following his senior season. 247 Sports ranked Arnold as the No. 9 overall recruit in the state of Nebraska for the 2017 recruiting class. Arnold also earned First Team Super State honors from the Lincoln Journal Star in 2016. He added First Team All-Class B from both the World-Herald and Journal Star, and received All-Area honors from the World-Herald. Entering his senior season at Gretna High School, Arnold was selected by the Omaha World-Herald to its "2016 Super Six" the top six football players in the state entering the 2016 season, and was described by the World-Herald as, "pound for pound, might be the state's most tenacious, most effective lineman." He played primarily at offensive tackle in high school but also played some guard. Arnold led Gretna to a No. 2 seed entering the 2016 Class B State Playoffs where they advanced to the state semifinals and a final 9-3 record. His junior season, he led Gretna to a 7-4 record and the state quarterfinals. He played for head coach Dave Shrader at Gretna High.
Arnold also received scholarship offers from Air Force, Army, Navy and Columbia.