Don't forget to consider: what can they really do for him with 158 score/potential??
If the program is designed for 130-ish children (who are for sure gifted, don't get me wrong)...maybe not getting in would not be a bad result.
before you end up fighting a big battle for entry, be sure to review the offerings of the program and what your son will likely need to see if they even match. best of luck!