I dont think you need Branall1 to have this question answered.

If you have been clean for that long, 1 joint will certainly leave your system in time. I've seen lots of guys do it like that with no problem. They did drink lots of water though as a precautionary measure.

If you are not an everyday smoker, it only takes a couple of days to leave your system unless you are a fat lard, because THC stores itself in fat and the "big fellas" have a much harder time cleaning their system.

I'll ask the same thing I've asked other kids that have been getting tested by their parents:

Do they make you piss in front of them? Are the test at the same day and time all of the time?

If they let you piss in the bathroom on your own you can use Quick Fix 4 synthetic urine and pass with flying colors. They provide you with a warmer that you rubber band around the bottle to keep it warm. $25 well spent. Takes about an hour for it to get to temp, or 7 seconds in the microwave for a quick primer and your good to go. You should be able to find this at your local head shop. If you cant find it at your local head shop, write a letter to your state senator requesting that all head shops in your area carry this product. Just kidding.....

Hell.... give them a cup full of Apple juice or Green Tea for that matter. Just find a small bottle (preferably a small plastic bottle like the QF 4 comes in, 2 oz. minimum!!) to keep it in and get a couple hand warmers at your local drug store to keep it warm.

Good luck my son..."Use the force!"