Charlotte Browning bounced back from national championship dissapointment to break a 22-year-old Sussex track record.
The Chichester High pupil set 2min.12.31sec in the under-15s' 800m at the Watford Senior Open to beat Donna Thomas' mark.
Browning was disqualified after finishing first in the English Schools' Championships last month.
But she bounced back to beat Thomas' record, who also attended Chichester, by 0.6sec.
Charlotte looks destined to end the season as the fastest British under-15 this year.
She was fourth out of 14 at Watford.
This weekend she defends her age group 1,500m title at the AAA Under-15 and Under-17s Championships in Birmingham.
Sussex athletes returned with four titles last year. Luke Davis took the under-15s' 3,000m race walk, Emma Perkins (Worthing) the under-17s' high jump and Amala Onuora (Eastbourne), the 100m gold and 200m silver.
Luke appears to have given up race-walking but Emma is on top form and eager to renew her battle with Jessica Ennis, from Sheffield, the girl who deprived her of the All England Schools' Championship title four weeks ago.
Amala missed out on a 200m medal at the All England but may race in both sprints at Birmingham.
Carley Wenham (Crawley), the Schools' under-15s' 100m champion who is undefeated over the distance this season, is favourite for her event.
Craig Ivemy (Hailsham), the Schools' under 17s' 3,000m champion, is up against Matt Barnes-Smith. He was beaten in the Home Schools' International by his Ipswich rival last month.
Craig was fourth last year with Barnes-Smith second.
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