My son is only in daycare (he's 2), but his teachers are ON-BOARD in a big way. They want to be educated about diabetes and what lows look like. My concern for you, which is the same for me, is that if he's been having lows, they need to recognize them (by him telling them or by checking his sugars) and treat. Have you considered changing his ratios? Lows can put him in a coma or seizure, and my intent is not to insult your intelligence, but THEY need to know that.
My daycare provider, and I'll tell you I'm sooooo lucky, is T1D. She checks his sugars. No one gives a bolus except my husband and I, but she does check his sugars. The other provider, who doesn't have diabetes, also checks. I've spent many hours and months with them, educating them on his target and what it looks like for him to be low and high. They can see the difference now and we talk about his day every single time we talk. He is not treated differently and checking his sugar takes 1 minute.
As a rule, even if they don't check his sugar, but they think he's low, they give him a quick 2 oz of apple juice. He perks right up and carries on with his day. Could the teacher check his BG? If the school won't allow that, is your son old enough to tell her that he's low? Could she then give him a small amount of juice? That amount would be what you would give him based on what you know about how he reacts to fast acting juice.
I think if she cares about him, she is probably willing to be even more educated. Once she finds out more info, she'll probably be more brave and more aggressive with his lows.
Good luck and I'm glad that you have at least one person who cares. That's better than 0!