in = is ( from now on )
So you were quite the precocious youngster, then?
Heck, all speed limit laws are ambiguous. So far as I know, there’s always a clause for “reasonable and safe speed”. If, for instance, a 65 MPH stretch of highway is glazed over after an ice storm, and you’re doing 40, you can still get pulled over for speeding, since 40 MPH probably isn’t a safe speed for a glazed road.
Why yes…yes, I was. But that’s a horse of a different color, now isn’t it??? 
FYI, here’s the law
Cal. Veh. Code § 22352
(a) The [speed] limit [is] (2) 25 MPH (B) When approaching or passing a school building or the grounds thereof, contiguous to a highway and posted with a standard “SCHOOL” warning sign, while children are going to or leaving the school either during school hours or during the noon recess period. The prima facie limit shall also apply when approaching or passing any school grounds which are not separated from the highway by a fence, gate or other physical barrier while the grounds are in use by children and the highway is posted with a standard “SCHOOL” warning sign. For purposes of this subparagraph, standard “SCHOOL” warning signs may be placed at any distance up to 500 feet away from school grounds.