Annabel Facey scored on a power play, assisted by Ella Woodhead, with 3:19 remaining to play to give the Gators (12-2) a 7-4 edge.
San Ramon Valley drew within 7-6 with 1:05 remaining to play. Woodhead blocked a shot in the field and SRV missed its final shot.
Sacred Heart Prep hosts Miramonte in a nonleague match at 4:30 p.m. Friday.
Girls Volleyball
In the West Bay Athletic League Foothill Division, Sacred Heart Prep (16-7, 7-2) beat visiting Mercy San Francisco 25-11, 25-14, 25-15 as Millie Muir recorded 36 assists and 12 digs.
Elena Radeff led the Gators with 20 kills and Iris O'Connor had 12 digs.
The Gators travel to play Harker at 6:30 p.m. Tuesday.
Girls Tennis
Sacred Heart Prep topped host Castilleja 5-2 at Rinconada Park in another WBAL match.
The Gators (8-5, 3-2) swept the doubles matches and got singles wins from Sara Quinlan and Katie Sinclair.