While you probably would be required by American Universities to provide for a evaluation services, I cannot stress how bad my experience with World Education Services has been. Take this with a grain of salt, since I'm sure other have great experiences. My evaluation was horribly done: WES graded my higher foreign grades, as a lower American equivalent then a lower foreign grade. In other cases, they had two different American grades for the same foreign grade. WhenI tried to get my grades reevaluated, they simply e-mailed me back saying no changes were needed according to their grading scale. Then when I tried pointing how they were not applying their own scale correctly and consistently, I got the same generic e-mail.
It took a credit card dispute and numerous complaints until they finally changed my grades two to three months later (much after application deadlines were due). Since they changed my grades so late, I had to pay for another company to do the job and pay extra for expedited service. I strongly suggest that anyone needing evaluations done go with a different company.