This might be a yearly thing, but it seems like home teams have dominated the biggest matchups of the season. Here are a couple that come to mind where either it was an upset or teams that are evenly matched.
St. Francis over De La Salle
Folsom over Pittsburg
Pittsburg over Valley Christian
Central Catholic over San Ramon Valley
Bellarmine over Central Catholic
Vacaville over Oak Ridge
Cardinal Newman over Vacaville
Del Oro over Clayton Valley
Granite Bay over Del Oro/Vacaville
Aptos over Palma
Salinas over Aptos
St. Francis over De La Salle
Folsom over Pittsburg
Pittsburg over Valley Christian
Central Catholic over San Ramon Valley
Bellarmine over Central Catholic
Vacaville over Oak Ridge
Cardinal Newman over Vacaville
Del Oro over Clayton Valley
Granite Bay over Del Oro/Vacaville
Aptos over Palma
Salinas over Aptos