Previously with Northampton Town, Blackwood joined the Gunners in 2007 but saw his two year stint with Arsene Wenger's side hampered by injury.
He appeared 12 times for the Emirates Stadium outfit last season, as the club won both the Premier Academy League and FA Youth Cup double.
Spurs also announced that talented twosome Sam Cox and Steven Caulker have signed their first professional contracts.
Cox, who can operate in both defence and midfield, started 22 of his 24 matches for the U18s in 2008/09, while centre-back Caulker featured in 31 of the Academy's 34 matches last season.
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