The youngster from the West Hill club in Hastings had his first bout in October 2019, which he lost on a close split decision.
But since then he has made quick and excellent progress and has won five of his nine contests.
In the recent English schools championships he won convincingly against opponents from Peterborough, St Austell and Walsall.
The national finals were held at Newcastle and Alagoa was unfortunate to be boxing one of the best junior boxers of the tournament in the shape of Archie Coates from Rainham in Essex.
Alagoa started well but got caught by a good right cross which knocked his head back and the referee gave him a standing eight count.
The bout continued and it was punch for punch before Alagoa took another right cross which made the referee step in and stop the contest, way too early in the opinion of his coaches.
Dave Bishop from the West Hill club said: “Jake can be proud of reaching a national final having had only nine bouts.”
West Hill Boxing Club has been going for more than 80 years and even stayed open through the Second World War.
It has a long history of producing national champions, finalists and England representatives, spanning many decades.
Bishop said: “We have around 100 members and a team of t10 qualified coaches. We are open four evenings a week and coach around 35 boxers per two-hour session.
“Through the Covid restrictions we did some socially distanced outdoor training and when we were allowed back in the gym we carried on with the socially distanced training until all restrictions were lifted and we could carry on as usual with padwork and sparring.
“I’ve been busy matching our show, which is being held at the Hollington Community Centre in St Leonards tomorrow (Saturday, December 4) at 6.30pm. I have boxers coming from London and all over the south east and have 18 top quality bouts matched.”
See more online at hastingswesthillbc.co.uk