The Liverpool-born left-back is in his seventh season as a Clarets, after signing a two-year scholarship ahead of the 2019/20 season.
The left-back joined Padiham at the end of September in 2019 on a months experience loan.
After a spell at Padiham, Armstrong then joined Clitheroe on loan for a month at the beginning of December.
Armstrong then returned to Philliskirk's side and featured a handful of times towards the end of the season, before becoming a regular part of the U18s' defence in 2020/21.
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