How do I get over my fear of the high jump?

Just this year at school we started doing high jump. The lowest is 90cm, and I'm still scared! My P.E teacher is strict and everyone in my class can do it. I'm just scared I will crash and fall, somehow I can't get my legs over it. I did it once or twice,but I'm so scared and I don't know exactly what it is. Can anyone help?|||Do a sky-dive,.