<p>hennes, you have to roll your own number. Track down the standard deviation, and use a normal distribution table. Make your son do it, to prove he deserves his math score ;-)</p>
<p>For the SD, an alternative approach is to find the SAT scores that match the 50th and 84th percentiles. The scores difference is the SD. If you are unfamiliar with Gaussian (normal) distributions, read the Wikipedia monograph for a painless review that will be adequate for your purposes.</p>
<p>After you find the number you are looking for, remind yourself that combined SAT scores can easily vary 50 - 100 points between sittings by chance, and so not to imbue the result with any magical (or absolutist) meaning.</p>