When I was first diagnosed (at age 16) I hated the thought of telling people. I felt awkward telling people. Very few of my friends knew and the few that did know didn't really understand. Then I had a massive hypo at school and needed help (ended up with 3 cans of diet coke and a packet of sugar free sweets before I got the can of full sugar coke I needed). I used to hide in the toilets and take my sugar levels and insulin or just not take them if there wasn't a toilet.
Then I met someone in another class who was Diabetic, had been all her life, and her attitude towards her Diabetes really woke me up. It was MY attitude towards Diabetes that was the barrier! I hadn't fully accepted that "Big D" was a part of me and I felt ashamed that I was Diabetic. Since then (sounds easier than it was) I have tried to change my attitude towards it. Most people don't have a problem or issues with you being Diabetic- sure there might be a few questions about it or the odd person who might start treating you differently, but the majority of the time, it is fine as long as you are fine about it. Would you feel awkward about telling someone you were a vegetarian if they were going to cook for you? Or if you had an allergy to peanuts? Being Diabetic might be a big deal to you, but to most other people, it isn't something that really concerns them.
Also, Maybe the people who you took you reading in front of did notice, but didn't think that you were comfortable talking about it. Maybe they misread your awkwardness for not wanting to talk about it.
On the other hand, you don't have to go around shouting to the world that you are Diabetic (I had a Diabetic friend who used to bring it up in every conversation). If someone notices that you are doing your blood sugars "Oh, I'm just doing my blood sugars. I'm Diabetic" No big deal, easy peasy. If a teacher calls you out on it and you don't want to announce it to the entire class, just say you have a medical condition that you could discuss privately.
It isn't easy at first., it doesn't ever really get to be easy, but it gets easier telling people. In the past I have told people in a round about way, talking as if I expect that they know: example if you are talking about watching something on TV, "I was so cross, I was enjoying it and then I had to go and take my blood sugars- darned Diabetes!!" "oh, your Diabetic?" "Yes, didn't you know? Anyway, when I got back I'd missed the results...". Sometimes they don't even question it, just accept the information or might talk to me afterwards.
As for the rushing off to the toilet around meal time- you wouldn't believe the number of people who used to think I had an eating disorder and were actually relieved when I told them I was diabetic!!