Mills-Shute was only beaten by Kendal’s Ben Winterburn in a strong field at the competition held at Tudor Grange Leisure Centre at the weekend.
The Plymouth student clocked 2:10.46 for the swim and then clocked 5:08.12 for the run.
In the under-19 boys’ category, Plymouth College had two athletes finish in the top 10. Tomas Maksimovic was sixth, with Tommy Osrin finishing 10th.
Jon Dobel came eighth in the under-15 boys’ event, with fellow Plymouth College pupil Christoph Lemken 18th.
In the girls’ section, Great Britain pentathlete Annabel Denton was ninth in the under-15 competition, while team-mate Anna Brauckmann was 11th in the under-16 girls’ event.
Mount Kelly also competed at the event in Birmingham.
In the under-14 girls’ category, Mount Kelly’s Amelia Riggott came fifth.
There was also a fifth-placed finish for Matilda Riggott in the under-11 girls’ competition, where team-mate Daisy Heal was seventh.
Fellow Mount Kelly pupil Annabelle Hess was 15th in the under-13 girls’ event.
Full results can be found HERE.