A trio in their early teens all crossed first in the Ness Cup mile handicap race at the Caledonian Ground.
The 14-year-old clocked a handicap time of 6min 09.65sec, an actual time of 5min 29.65sec, to win the nearly 100-year-old trophy.
It was an impressive run from the young trio, who took the lead from front-marker Philip Morris after 600m.
Collard (13) and Carswell (14), who started together, ran down Morris and remained together for the majority of the race.
Bolter followed, although he could not pull in the leading duo.
Collard broke away with 200m left and claimed first place in a handicap time of 5min 59.72sec, 3.5sec ahead of Carswell.
Bolter finished third, holding off a strong finish from Caversham's Ben Pigou, who came charging down the home straight 3sec back.
Queenstown Athletic's Colin Kirkpatrick had the fastest time of 4min 26.80sec.
In other events, William Scharpf edged Josh Hou in a tight 800m. Scharpf ran 1min 57.57sec to edge Hou by 0.08sec.
Nirvana Hepi-Breen also had a standout day, throwing 44.46m to break the women's 14 and 15-year-old Otago hammer records.
Dyani Shepherd-Oates also had another strong outing in the hammer circle with a throw of 47.43m.
In the shot put, Jade Zaia won the men's grade with 13.64m, while Zharna Beattie impressed in the women's under-18 with 13.08m.
Beattie also won the women's discus with a distance of 37.92m.
In the long jump, Shay Veitch jumped 6.80m to edge Invercargill 15-year-old Quinn Hartley, who managed 6.76m. Hartley also cleared 1.95m in the high jump.
Veitch also claimed the 100m-200m double with times of 11.17sec and 21.98sec.
Rosie Elliott was the fastest woman in both sprints in times of 12.16sec and 24.43sec.
