They started by overcoming a strong Judd side 9-8, holding on to their slender lead by playing the more controlled netball in the second half.
They secured tight wins in physical encounters with Benenden (10-7) and Tunbridge Wells Girls’ Grammar (12-8).
TGS beat St Lawrence easily 16-6 before finding tougher opponents in Sevenoaks, who they defeated 10-8.
The team completed a full set of victories by overcoming Hayes (15-8) and Walthamstow Hall (9-2) to secure the trophy ahead of The Judd School.
Both teams now go on to represent Kent in the LSE Regional Finals in Middlesex on January 27.
Assistant Headteacher Adrian Pitts said: “It was a fantastic achievement from a team whose core players have now been county champions at every age group apart from one.
“I cannot praise them enough for their continued commitment to training and their wonderful team spirit which shines through every squad member old and new.
TGS’ Under-16s played every game on the court ahead of the Under-19 matches which meant that both teams could cheer each other on.
They began with an 11-9 defeat to Highworth Grammar from Ashford, a strong team they had already played in the qualifying tournament.
A 9-9 draw against Benenden came next, and the result was to prove decisive when it came to the countback at the end of the day.
The Under-16s managed to post their first win against Tunbridge Wells Girls’ Grammar 9-4, but that was followed by another draw, 6-6 against Sevenoaks.
TGS were leading throughout the match until the very end, but were undone by basic passing errors.
Determined to play at the level they knew we were capable of, they lifted their game to record strong wins in the final three matches against Rochester Grammar (14-6), Bromley High School (8-4) and Walthamstow Hall (16-7).
They needed Highworth to beat Benenden if they were to qualify for the Regionals as runners-up. But the Ashford school lost, having won all their matches up to that point.
That pushed TGS into third place behind Benenden, who went through with a superior goal average.
Emily Cross, the Under-19s captain, said: “Overall, it was a really enjoyable day and both teams performed exceptionally well.
“There were challenges but with the support and confidence in each other we managed to work through them and came out as champions.”
