You can fight this in court but it is your word versus the officer. The officer in question will most likely appear at your court date and make a case against you. Because this ticket is a moving violation, in most states this will mean points on your license. You should consult a lawyer, for about 3x the cost of the ticket a lawyer may be able to plea down to a non-moving violation with no points on your license.
In California, the fine for passing a school bus that's stopped with flashing red lights is $1000.00
$250
Red lights flashing on a school bus mean remain stopped until they are turned off.
You should remain stopped until the bus's red lights are no longer flashing.
Stop until the red lights stops flashing
2,500
$1,000
If it's a school bus, whenever the lights are flashing.
STOP!!
$300.00
$250 for the first offense. You must come to a complete stop and wait for the bus to turn off their red flashing lights before you are eligible to proceed
Yes, you can get a ticket for passing a school bus if a school parked in a shopping mall with flashing red light on but no driver nor students.