38-40 hot should be good.
Keep in mind that at the start of a school or in the damp the tires will not heat up as much so you may want to start at like 32 ft and 34 rr. As the driving gets more agressive, just manage to the hot temps after the car comes off track. Watch for one corner or side to get warmer and more pressure than the others due to the particular track or the car. Note that and keep in mind for when you rotate tires or go out for the first time in the morning.