Angmering pupil Emma Perkins, whose heroine is Olympic heptathlon gold medallist Denise Lewis, has been selected for England.
She was selected after finishing second in the All England Schools Combined Events Championships at Birmingham.
Emma, 15, clocked a personal best 11.75sec in the 75m hurdles, the first of the five disciplines.
She hurled the shot 9.01m and was one centimetre below her best with 1.67m in the high jump.
In windy conditions, her long jump of 4.73m was below this season's form.
As they lined up for the 800m, Emma was third and out of touch with leader Phyllis Agbo (London).
She stuck to second-placed Louise Hazel (Cambridge), a useful two lap runner.
They left Agbo behind and Emma set another personal best with 2min.36.35sec to amass a total of 3,091 points for the silver medal behind Hazel, with Agbo third.
The winner totalled 3,207 points, just below Emma's Sussex Championship record of 3,236, but conditions at Birmingham were tough.
Emma said: "I felt a little frustrated and maybe disappointed, but I had gone to Birmingham with just an outside hope of maybe getting a medal. I'm overjoyed, really.
"I'm delighted to be competing for England at Kelvin Hall, Glasgow in December."
Emma was glued to the television as Lewis won in Sydney.
"I could really feel for Denise. I could hardly watch but she knew what she had to do and it was tremendous. We were shouting at the television set and I felt as if I had run the 800m at the end."
Blatchington Mill pupil Jenny Bliss (Brighton and Hove) qualified for the under-15 pentathlon final, finishing 12th of more than 40 with 2,657 points.
In the under-19s' heptathlon, The Weald pupil Lucy Newman, from Billingshurst, battled through a thigh injury.
The Horsham Blue Star athlete was 21st out of the 28 with 3,269 points in her first year in this age group.
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