One's personnel file does not follow him/her from school system to school system. I have participated in the hiring of many teachers and coaches, and not once did the interview team see nor ask for the job seeker's file from another system. So, the incident being put into his file, basically means nothing unless a school system wants/needs to get rid of a tenured teacher, in which case, they must provide documentation of poor performance, insubordination, etc. For a non tenured teacher, the school system may use the incident as a reason to deny tenure, but by law, they may not disclose the reason for denying tenure.