It will likely be a good experience for him.

You could have him practice using a calculator since you are allowed to use one on the test. There are some practice questions you can google to give him an idea of the format. Our experience was that those were a tad easier than the actual test, but you don't have to tell him that.

We tried to keep it as low pressure as possible, and DC did have a lot of fun taking it. The results were very helpful to us, and for the school.