Well, I wasn't in grade school, but I was in college... *NO, it's not what you think*
I had been in marching band camp all day and ate at the dining hall with everyone else. Then in the last few minutes of break time I had left, I went to visit the daughter of my high school English teacher (He had asked me to watch out for her.) She was sick in bed, and said she had fallen in the bathroom and hit her head when she felt faint. I encouraged her to go to the student health services, which was just a few hundred feet away from her dorm.
As the evening practice went on, I started feeling really weird -- hot flashes, dizzy, definitely sick. I ran out of practice and went to the bathroom, where I spent some time taking deep breaths and trying to compose myself. I finished practice, but we had uniform fitting afterwards. I felt so sick I thought I was going to pass out. When I was standing there with one of my classmates fitting my uniform, I actually told her to hurry up because I was going to faint. I think she could tell how sick I was because she had this weird look on her face. (Not to mention how I must have looked.)
Well, I didn't faint there, but as I walked out the back door of the rehearsal hall, I collapsed. Luckily I had made it up the cement ramp and on to the grass -- I was going to walk next door to campus security and ask for a ride to my dorm because I was so sick. I didn't make it that far.
So there I was, lying face-down on the ground next to a puddle of vomit when the campus security officer drove up (probably the end of his shift) and found me. I was semi-conscious and heard him say "Oh, &%[email protected]
not another one!" and call for the ambulance. Within a few moments I was conscious enough to speak and I said, "I swear I'm not drunk." (The beginning of the school year at U.D. was notorious for alcohol poisoning cases.) He said, "I believe you... I've been taking sick kids to Laurel Hall all night (the health service.)"
So I got a free ambulance ride to Laurel, where I was put in a triage area (luckily I got to lie down on a stretcher instead of having to sit in a hard chair, because I had passed out) and... threw up a half dozen more times. Every time I was sure it would be the last time, but once I was vomiting bile I realized it wasn't going away.
The State of Delaware conducted an investigation of nearly 100 cases of acute gastroenteritis on campus in two separate outbreaks. They were unable to determine the exact cause, but believe that it was caused by a Norwalk-type virus, possibly transmitted through cross-contamination between iced food (i.e. chilled, not frozen.)
Oh, BTW... After staying overnight in Laurel, I woke up in the morning to find my English teacher standing in the hall near my cot (that's how bad it was, some of us slept on cots in the hallways)... His daughter had followed my advice and was in a bed nearby. But both of us had been so sick that neither knew the other was there.
It took me almost a month before I could eat normally again.