NO! You can NOT proceed through while the crossing guard still has their sign up. Most law enforcement agencies have zero tolerance in this, and many crossing guards will report the vehicle and driver immediately.
In my agency we show no mercy to drivers who pull this stunt or drive without due regard for the safety of our kids before and after school and you will get tagged for everything we can find. Oh, that was the policy in my last agency as well. I suspect it is similar where you are.
2815. Any person who shall disregard any traffic signal or
direction given by a nonstudent school crossing guard, appointed
pursuant to Section 21100, or authorized by any city police
department, any board of supervisors of a county, or the Department
of the California Highway Patrol, when the guard is wearing the
official insignia of such a school crossing guard, and when in the
course of the guard's duties the guard is protecting any person in
crossing a street or highway in the vicinity of a school or while
returning thereafter to a place of safety, shall be guilty of an
infraction and subject to the penalties provided in Section 42001.1.
- Carl