Please note, the field is not at the high school but is behind the middle school which is just down the road from the high school and on the other side of the road. 
The easy way is to go I 64.
From Charlottesville: Take I 64 west
Get off @ the Crozet Exit (should take approx. 20 min from Ch-ville to field)
take right @ end of off ramp onto 250
Go less than 2 miles- 2 traffic lights.
Take left @ 2nd light into parking lot between 2 schools.
Sorry but I don't know the road names from UVAs field.
From there you are close to the 250 by pass which will take you to I 64.