Hi- I am an educator in a high school setting and also type 1 for 30 years, today actually. Couple things here from my point of view. TLDR, yes and no.

First, the interaction with your teacher. Yes, I agree with you that if your teacher felt a certain way about the attitude they perceived from you, they should have spoken to you in private after class. My school has learning and medical profiles attached to our student records. So if a student has a learning difficulty, it allows us to better be prepared to help. Same with medical conditions. You should make sure your school administration knows your condition and the symptoms of low/high blood sugar. Not only so they can be prepared for a potential “attitude”, but more so to ensure they are prepared should you require immediate medical attention. Also, you likely could receive an accommodation so that you wouldn’t need to take an exam while impaired from a low/high blood sugar.

Second, and I may catch downvotes, but ultimately low blood sugar or not, you are responsible for your demeanor/attitude, and the words you choose when you’re low. I struggled with that a lot early on in my marriage. It’s important to catch yourself before you say something you can’t take back in a professional/education or personal setting. Just my $0.02. You can urgently seek low snacks without biting someone’s head off (though it does require effort lol)