Probably Many Times
I'm sure I cried many times at school during the years I went, but one time in particular springs to mind. It was probably the first time.
Kindergarten. We had this tub of sand that we were supposed to write our name in with our finger. I remember panicking because I couldn't remember if the curved part of the J was supposed to point to the left or the right. So I cried.
God, what a baby. I was only 5, though.