Am I a victim of age discrimination?

I am 52 years old and work as a teacher for a private school, and have been with the school for three years. During that time, I have seen several incidences of young mothers receiving better schedules, free or reduced child care, and higher pay. Recently, I was very upset when I had scheduled a day off for vacation and my younger parent/coworker called in to work for the 14th time in two months. I received a call that my sister was being life-flighted to Hermann in Houston with an aneurysm. There was no way I could be at work. I called my boss and in my anxiety and frustration, told her that I didn't think these things were fair. Please note that I have never been counseled about major problems with my classroom until this incident. While I was out that day, another coworker, who was upset about being taken out of her classroom, evaluated my classroom. When I returned to work, I received a lengthy write-up full of accusations that are not true. My younger coworker received no write-up, although the classroom responsibilities are supposed to be shared. Discrimination and retaliation are what I believe is happening. What should I do?