Hillsborough is part of the San Mateo High School District. You can find information about at HS within the district at http://www.smuhsd.org.
There are several great public HS in the district and several of them are among the best in the State and rank highly nation wide. These are: Burlingame HS (this one serves Hillsborough), Mills HS, Aragon, Hillsdale and Sana Mateo - all in San Mateo. At least 2 of them Burlingame and Mills) have AP scores above 800 (i.e. they graded excellent.
The future is bright to. San Mateo county residents voted in $298 M bond measure (Measure M) to renovate high schools within a district. I am very involved with high schools in our district (I was co-president of PTO at Mills and am part of the Citizen Oversight Committee for Measure M. Don't hesitate to ask me any question regarding schools you might have.
Please check http://www.newsweek.com/id/39380/?q=2008/rank/201/
for the US ranking (BHS is 245 and Mills 251)