Don't save. While the math score is very good for your son's age (Congrats on qualifying for SET!), he will be able to repeat this or score higher when he is in HS. I was about to say that CR and W will also rise as he gets older, but then I remembered that there will be a new SAT format in a few years, so kids in his class will not be sending the 2400 SAT format scores to colleges.
I wouldn't really trust the superscoring thing - while the colleges do this, one sitting with much lower scores will look weird. If he takes the ACT, I understand that those scores are saved regardless of when he takes them. However, I don't think that you need to send the ACT scores prior to HS even if the colleges say to send all scores - they really don't care what you did in 7th grade.
