Give yourself permission to take a mental health day if you need it. It is much better to take a day off than to go into school angry or sad or frustrated. It is also ok not to leave plans. It’s not ideal, however if that is what is stopping you from taking a day off that you really need, then don’t send in day plans. Use your emergency plans – this is what they are for.
In the past, it was taboo to take a day off if you weren’t “really” sick. This lead to teachers coming into school when they had pneumonia or were having panic attacks. This is not ok and now we know it’s not ok. In fact, it is far, far preferable to take the day off when you need it. Or two.
If you are having difficulty with an administrator about this, call your union rep – that is what they are for! Also, if you find you are taking many mental health days in a month, go and talk with your doctor. You may need more than just a day off in order to have good mental health.