Weir, representing Birmingham University, finished second in the women’s 2,000m steeplechase.
The Great Britain under-20 international was in with a chance of winning until the last water jump, where she lost ground on St Mary’s Emily Moyes.
Moyes, who had finished third behind Weir and Tavistock’s Tess Masselink in the 1,500m steeplechase at last year’s English Schools’ Championships, won in a BUCS record time of 6:35.07.
Weir finished in 6:40.45, which puts her third in the 2017 UK rankings. Bangor’s Laura Riches was third in 6:45.41.
Meanwhile, Weir’s City of Plymouth team-mate Poppy Tank set a new 1,500m PB in America at the weekend.
Tank, who is studying at Utah University, clocked 4:31.00 at the Oregan State University High Performance Meet. That was more than two-and-a-half seconds faster than she had previously run over that distance.
It was Tank’s fourth PB of the year, having already set new best marks in the mile, 3,000m and 5,000m.
There were also impressive performances this weekend for City of Plymouth multi-eventers Emily Bee and Sammie Harris.
Both competed in the Somerset Schools’ Combined Events Championships at Street, which attracts many of the UK’s top athletes.
Bee won silver in the under-17 heptathlon with an impressive score of 4,421 points, while Harris finished seventh in the same competition with 4,125 points.
The duo are both in their first season at under-17 level and are now ranked second and seventh in the early heptathlon UK rankings.
Bee clocked 11.99 seconds for the 80m hurdles, achieved 1.57m in the high jump, set a PB in the shot of 10.15m, ran a PB of 26.73 seconds in the 200m, jumped 5.38m in the long jump, threw 23.72m in the javelin and finished with a time of 2:35.67 in the 800m.
Harris clocked a new PB of 11.87 seconds to win the 100m hurdles, leaped 1.48m in the high jump, threw 10.40m in the shot, ran 27.38 seconds in the 200m, recorded 5.26m in the long jump, threw a new PB of 24.07m in the javelin and ran 2.46.83 for the 800m.
Events on the second day at Street were not helped but the weather.
As well as both being ranked in the top seven UK under-17 heptathlon rankings they are also in the top six for 80m hurdles. Bee is ranked fourth in that event this year with 11.82 seconds achieved at Exeter at the start of April, with Harris moving up to sixth with her 11.87 this weekend.