Several former senior international players will be included in the hundreds of old boys of both schools who will be present in Brecon for the 2.30pm kick-off.
The first match between the schools was back in 1879 and Llandovery are well in the lead in the series, but are likely to be without their skipper and Schools international lock Alun Wyn Jones, who has a leg infection.
Brecon centre Duncan Jones will be hoping to lead his side to their first success in the annual match since 1998.
