There are basically 3 ways that many NCAA programs measure it. From contact on right side...from contact on left side....and standing on the back edge of the plate and when the lead foot hits the ground. Telling us how you are asking would make a big difference in the times.
We did our times from back edge of plate. Fastest time we had was a 3.5 was an 11yr old. My Dr ran a 3.6 and she is only 9
I've read average high schoolers is at 2.8-3.0 So I thought mine ran fairly good.