Dd#1 had MAPs scores in the 240 range in 4th grade, so I know that the test does go up to around 250. He should still have some room for growth to show and I believe that the numbers go up more slowly as you get into the highest numbers.

That aside, you can try ITBS or an individual achievement test like the WJ-III or WIAT. Also, he could do above level testing probably next year through talent search (EXPLORE) to see how he compares to kids in grades above his.