[2] However, by the 1900s Celtic manager Willie Maley was only using a small, if versatile, squad of players, and the decision was made to stop fielding a reserve team altogether.

[5] Malky MacDonald, Johnny Crum, George Paterson, Jimmy Delaney, John Divers and Willie Buchan all emerged during this time from the reserve side and went on to form the nucleus of the Celtic first team that won the league championship in 1936 and 1938, and the Scottish Cup in 1937.

[5] In 1936, Celtic fielded trialist Mohammed Salim in two Alliance league matches, with him becoming the first footballer from the Indian sub-continent to play for a European club.

The subsequent years into the 1950s saw various changes to the leagues, but Celtic's achievements at reserve level were undistinguished, with two fourth-place finishes in 1952 and 1954 their highest positions.

Future star players such as Paddy Crerand, Billy McNeill, John Clark and Bertie Auld all emerged at Celtic during this time.

[8] Although Stein left in 1960 to manage Dunfermline Athletic,[9] promising players continued to emerge from the reserves, such as Bobby Murdoch, Jimmy Johnstone and George Connelly.

Several became regulars in the first-team side, winning major honours and going on to represent Scotland at full international level, most notably Kenny Dalglish and Danny McGrain.

[2] Key players continued to emerge from the youths and reserves; Roy Aitken, Tommy Burns and George McCluskey in the late 1970s,[12] and Pat Bonner, Charlie Nicholas and Paul McStay in the 1980s.

[16][17] During the 2010s, James Forrest, Callum McGregor and Kieran Tierney all progressed as youths at Celtic and became established first-team players at the club.

[20] At the end of its first season (2018–19), Celtic – along with several other clubs – intimated that they would withdraw from the Reserve League to play a variety of challenge matches.

A plethora of cups were introduced during the 1880s but the advent of professionalism a decade later put pressure on club finances, and during the 1890s these tournaments gradually fell away.

[27] In the 2016-17 edition, Celtic U20 won their opening tie against Annan Athletic and then eliminated Cowdenbeath (both of the fourth level) before being knocked out by the then-League 1 club Livingston; they progressed further than all other Under-20s teams.

[28] Celtic's U20s were the first Scottish participants in the NextGen Series - a youth tournament based on the UEFA Champions League.

[32] In the Youth League, the Group Stage mirrored the tough draw in the senior tournament, and Celtic collected just one point and finished fourth.

The academy also works in partnership with St Ninian's High School in Kirkintilloch, where players of secondary-school age benefit from nine coaching sessions per week.

[39][40] In 2017, the Celtic academy was one of eight across the country designated 'elite' status on the introduction of Project Brave, an SFA initiative to concentrate the development of the best young players at a smaller number of clubs with high quality facilities and coaching than was previously the case.

In 2019, Celtic announced plans to redevelop their older Barrowfield training ground in eastern Glasgow near Celtic Park for use by the academy sides and their women's team, including an indoor pitch and a matchday venue, augmenting the Lennoxtown base which would continue to be used by the first team squad.

[45][46][47][48][49] In July 2021, it was announced that the men's B-team (as well as the women's team) would play the majority of their home fixtures in 2021–22 at Airdrie's Penny Cars Stadium.