They were called up to represent their country in Dundee over the weekend after being selected at Boxing Scotland’s high performance centre last month, smashing the assessment process.
Both boys, 13, had won the Scottish championships at their respective weights previously for the Grangemouth-based club.
On Saturday, O’Reilly boxed fellow Scotsman Lucas Ewan in the semi final and won by a second round stoppage.
Elsewhere, Retson boxed Tom Jones of Wales and lost his bout on a 3-2 split decision.
In his fight, he started slowly in the first round but stepped up the pace throughout the second and third round and was unlucky not to come away with the decision.
Retson took home a well earned bronze medal.
In Sunday’s final, Thomas boxed the English champion Tom Connors.
This was a tough match between two of the best youngsters throughout the UK.
Connors, who was a southpaw, picked up the lead by narrowly winning the first round.
O’Reilly stepped it up in round two and started to land his combinations.
Going into the last round it was one each on the judges’ scorecards.
It came down to the final round and he set a pace and won the majority of the exchanges, winning the bout on a 3-2 split decision, he became the new GB 52kg weight-level schoolboy champion.
Speaking to the Herald, head coach Sam McLeod said: “I am very proud of the boys’ achievements and even more so how they carried themselves throughout the whole tournament.
"They did the club and their country proud and I am certain this won’t be the last time we see them represent their country.”
Scotland claimed 18 GB gold medals this season, with three elite GB champions crowned earlier this year in Cardiff.
Scotland finished this weekend’s GB Schools competition with a haul of 5 golds, 7 silvers and 13 bronzes.