The 20-year-old striker joined Oxford United on a season-long loan last week, and in addition to making 17 appearances for the Spurs first team, Scarlett scored 12 goals in 14 games for the England Under-19s, and six in 16 matches for the Under-20s.
Scarlett has also had loans stints with Portsmouth and Ipswich Town.
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U’s head coach Buckingham said: “It’s great that Tottenham have trusted us with his development. He’s a young, exciting English centre forward with a lot of caps for the England age group teams.
“Anyone that’s been fortunate to watch him in that space, he’s certainly showcased his power and what he’ll bring to us.
“His experience in the last two years when he’s gone out on loan, he probably hasn’t got as many games as he’d have wanted, and the way that hopefully he can here, that’s the platform we’ll try and provide for him.
“There’s a lot of history in terms of this club helping develop young players, with Fin Stevens being the latest off that conveyor belt for loans.
“We’ve also got a good track record of working and developing our own. You only have to look at people like Tyler Goodrham and the others that have come through of late, so hopefully it’s a good breeding ground and environment for him to develop, while aiding us to get where we want to get to.”