I Have Almost Fainted

This happened in my last year junior school, I recall having to sing a group song with the rest of my class for some presentation we were doing. The teachers wouldn't let us sit down or anything because apparently singing sounds better when you're stood up (I guess that makes sense) so we all had to stand. Towards the end I started to get lightheaded and I broke out into a cold sweat. I wasn't exactly sure of what was going on, so it wasn't until my friend told me I 'didn't look too good' that I realised I should do something. I asked the teachers if I could sit down but they simply said "you can wait, it's only 5 more minutes" I tell you if I had waited I would have passed out then. Eventually, as I started to see double I decided to lie down on the cold floor. Despite being scalded by teachers it worked and the dizziness, sweats and double vision all went away