yeah! Real perfect 2400 scores are pretty rare. Around 300 every year. Then there are also super-scored 2400, combined highest section score of different sittings. Don't know how many of them each year.
Ania, my older daughter is already in college. My younger one is a HS senior this year, in the middle of college application right now. For some reason, I had the impression that your oldest son is also a senior, may be I remembered wrong.
As for your question about ACT, I would think that they keep all the scores (not sure about the score before high school), you may want to call them just to make sure. CTY summer camps are more suitable for middle school kids. For high school kids who are interested in math, there are a number of more serious camps such as PROMYS, Canada/USA Mathcamp, SUMac, etc. They usually require entry test (fairly difficult) which weeds out anyone who are not serious.