There are several steps that a professional can go through to resolve a "workplace problem" And you're doing the first and most important, you're establishing exactly what you can and cannot legally do about the problem. Are there laws or restrictions in the workplace that will protect you from unfair treatment. You have an answer. Whether or not your case will fall into one of the rather rare circumstances where it would be illegal to treat employees differently, your next step is exactly the same.
You must look at your behavior. Is what you did and got in trouble for, REGARDLESS of what someone else is doing and getting away with, appropriate for you to do, and the best way to achieve whatever it was you were trying to achieve. Even if this is a rest room break, look only at your own situation. Is there someone you should have asked to take over supervision of your class? Is there a procedure in place to handle this? If so, did you follow it? What would you rather have go on instead? In other words, would it be appropriate if you and the other people behaved exactly the same and all left your classrooms for up to thirty minutes at a time unsupervised? Do you want this to be okay, or do you just want to make sure that other people get in trouble for doing it, the same as you did?
If you really feel that you were treated unfairly and that you are being treated unfairly in an on-going manner, that you have a legitimate complaint instead of a feeling, you will next need to try to solve the problem at the lowest possible level. In other words, you reasonably and professionally inform your supervisor of the problem you believe is occurring (that you are being treated differently than your co workers.) Even in EEOC related grievances where a complaint is filed, it is necessary for the person complaining to make some effort to resolve the situation at the appropriate level BEFORE they take it higher. Else the supervisor and certainly the next level up, they can say, "We didn't even know there was a problem, and if we had known it, we'd have fixed it!" And they're completely absolved.
So your first step, if you wish to complain about being singled out and treated differently for what you believe to be an illegal reason would be to bring this to the attention of your supervisor and attempt to get the problem resolved. If they refuse to listen to you, or retaliate by firing you, of course you'd have a reason to take the issue further, and would want to file a complaint with EEOC. Remember, not all singling out or treating differently is going to be illegal. If you make a big deal and complain, and you have no union to protect you, and no real grievance procedure, your employer in an "at will" state could very well make you an ex-employee simply because you are complaining about this. In an at will state, a person can be terminated for pretty much any reason, fair or not, reasonable or not. Unemployment insurance if terminated without a good cause is pretty much the only recourse. Make sure you have a legitimate complaint and that is something the employer could reasonably resolve. It doesn't seem to me that demanding to be "treated the same" as other teachers who are getting away with something that is probably not a good thing isn't a reasonable request. Perhaps asking the administrators to get you some classroom help so that you could take necessary breaks would be appropriate, regardless of what others are doing.
Many times in school systems with tenure, the most short term, untenured teachers do not have the same leeway in their behavior as the long term tenured teachers. That's just the way it is. They're going to be testing you and determining who gets to get into that job security situation, and they want very much to get rid of the people who are going to be problem employees before they have taught long enough to be tenured. That could be part of the issue and the reason you are treated differently.