Education
Jack attended Bellevue High School in Bellevue, Washington, where he was a letterman in football and track.
Jack attended Bellevue High School in Bellevue, Washington, where he was a letterman in football and track.
He played college football for the University of California, Los Angeles Bruins. In his first season, he was named the top freshman college football player in the Pac-12, receiving honors both on defense as well as on offense for his work as a running back. As a sophomore in 2014, he was named an All-Pac-12 linebacker for the second straight season.
His season ended prematurely in 2015, when he suffered a season-ending knee injury.
He withdrew from University of California, Los Angeles to focus on his rehabilitation and prepare for a professional career in the National Football League (NFL). In football, he played exclusively as a running back through his sophomore year, before also becoming a linebacker.
As a senior he had 98 tackles and 24 sacks, leading his team to a 14–0 record. He was also on the track & field team
He earned a fourth-place finish in the 400-meter dash at the 2013 Washington 3A State Meet, recording a personal-best time of 49.05 seconds.
At the 2013 3A KingCo Championships, he took bronze in the 200-meter dash event by clocking a personal-best time of 22.12 seconds. Considered a four-star recruit by Rivals.com, Jack was listed as the Number. 16 outside linebacker in the nation in 2013.
He chose University of California, Los Angeles over offers from Florida State, Arizona State, Stanford, Washington, and Utah.
As a true freshman in 2013, Jack played in 13 games, starting 12 at linebacker and one at running back. He finished the season with 75 tackles, the second-most ever by a University of California, Los Angeles true freshman behind Kenny Easley"s 93 in 1977.
Jack also added two interceptions and one touchdown on defense. As a running back, he had 267 rushing yards on 38 carries, averaging over seven yards per carry, and ran for a team-leading seven touchdowns in five games on offense.
The Bruins had been short on running backs with starter Jordon James out with an ankle injury.
With the offense still depleted in the backfield and with Coach Jim Mora playing mostly a nickel defense against Arizona State, Jack started and played exclusively at running back against the Sun Devils, carrying 16 times for 86 yards and a touchdown in a 38–33 loss. He also earned Freshman All-American honors by The Sporting News in 2013. In his sophomore year in 2014, he was named to the All-Pac-12 second team as a linebacker for the second straight year.
He also continued to see time as a running back, carrying the ball 28 times in nine games.
On September 22, 2015, during a routine practice, Jack tore the meniscus in his knee while performing a non-contact drill, and a statement was released from coaches stating that he would not return for the remainder of the season. On October 6, Coach Jim Mora announced that Jack had withdrawn from University of California, Los Angeles to focus on his rehabilitilation and entering the 2016 NFL draft.
His injury had occurred two days before the start of the fall quarter, and he had already fallen behind in his classes while rehabbing from his knee and coping with his short-term immobility. Entering the 2015 season, Jack was widely considered a first-round draft prospect.
2016 NFL draft
In early March 2016 Jack was predicted to be a top 10 pick in the 2016 NFL Draft, with many experts placing him as high as 5th.