The 16-year-old defender was named in the League One side's match-day squad on multiple occasions last season.
Academy manager Mark Harrison said: "We are delighted that Josh has joined us.
"He is a centre-back with an awful lot of potential who had attracted a lot of interest and has also captained England at U16 level.
"We would like to thank Fleetwood Town for their professional manner during the process of Josh joining.
"We look forward to seeing how Josh develops over the next few years."
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