They won two golds and two silver medals on Friday evening at Ponds Forge.
Amelia Riggott and Jacob Newcombe both claimed titles at the national event.
Riggott took victory in the 14-year-old girls’ 50m breaststroke with a time of 34.50 seconds.
Newcombe’s success came in the 17-year-old boys’ 100m backstroke. He clocked 58.12 seconds.
There were silver medals for fellow Mount Kelly pupils Tom Brew and Lewis Smart.
Brew clocked 2:07.23 minutes to make the podium in the men’s 200m butterfly, while Smart’s medal came in the 17-year-old boys’ 50m breaststoke with a 30.20 second swim.
There was also a silver medal for Devonport Royal swimmer Aiden Symons-Brown.
Also on Friday there were finals for Plymouth Leander’s Sean Gray, Joseph Thompson, Haydn Woolley, Isobel Bryant and Tobias Fredericks and Mount Kelly’s Katelyn Bergin, Louise Edmunds and Samuel Pease. Devonport Royals Abi Daly was also a finalist. She reached the women’s 200m MC freestyle and 100m MC butterfly finals.
Meanwhile, former Plymouth Leander and Plymouth College swimmer Ruta Meilutyte made the final of the 50m freestyle at the European Championships in Glasgow.
Meilutyte is better known for her prowess in breaststroke, but she produced two solid freestyle swims of 25.20 and 25.04 seconds to reach Saturday’s final.
She will also swim in the 100m breaststroke heats on Saturday – the event where she won Olympic gold in 2012.
Mount Kelly College pupil Federico Burdisso will also be in action at the European Championships on Saturday. He will swim in the 200m butterfly.