How about this "Because my child,_____________________ , continues to experience difficulties in school I am requesting an immediate re-evaluation in the areas of ______________________________________ to determine whether the current IEP is appropriately addressing his needs. My reasons for this request are: ________________________" That should get the ball rolling. It is simply revising the sample letter you looked at, you would just have to type the whole thing yourself. Hope this helps. It is what I would do.