Here's a link with the San Mateo County API Scores:
and here's the school boundary for San Carlos:
As Raziel correctly states, each school district has their own websites as well, which are good resources. One important thing to remember is that certain schools may be impacted (there are a couple in San Carlos) so just because you buy into a particular neighborhood doesn't mean you're guaranteed admittance to school district that you're zoned for. Be sure to check before you buy.
Hope this helps!