You should never use Western Union to pay tutition fees, unless the school doesn't allow anything else.
With Western Union, their conversion rates are sky high and you would be paying $3000 - $6000 more than if you converted your money at a reputable source before transfering it. Also, I have heard stories of Western Union transfer being much slower than normal wired transfer.
My recommendation is for you to find a place to convert your money at a good rate, then send this converted money to the school through wired transfer.
