You should file reports both at school and with the union.
It is important to file safety/incident reports with the union because it lets us know what is taking place inside of your building. If you do not report incidents to the union, most likely we will not be notified. Reporting incidents helps the union keep their finger on the pulse of your school. You can use the union's online incident report to file one.
All incidents must be reported as per Chancellor's Regulations. All incidents should be reported to an administrator and then be reported onto the DOE's Online Occurrence Reporting System (OORS).