Sure you're not running into this annoying 10.9 bug? have you actually done a get info on the HD?

https://jamfnation.jamfsoftware.com/discussion.html?id=10555#respond

I'm getting the info from the laptop itself. I saw one of your post on that thread, Let me try try running this on a few laptops.

find /var/folders -name "*.iscachebmp" -type f -exec rm -v "{}" ;

Another thing to try is to force Spotlight to rebuild.
Often that is the cause of the discrepancy being reported in disk space utilities.

@CasperSally You're were correct. It was the cache files filling up. I have a smart group and a policy that runs a script. Its been working great! Thank you!

@boettchs I have tried that first but found out that it takes awhile before re-indexing is completed. Students aren't logged in long enough to complete. But the solution Caspersally mentioned worked.

@Johnny.Kim - good you got a solution. Indexing is indeed a slow process - especially if there's a lot of data on the Mac. Glad you got it sorted.

beware if you're running find /var/folders -name "*.iscachebmp" -type f -exec rm -v "{}" ; as an execute command on a policy, which worked for me in 9.32, appears broke in 9.65. Running it as a script instead works.