I don’t see anything about. NJ High School. The NJ in NJHS is National Junior…I believe.
Perhaps this poster can clarify.
Hoping these twins cast a broad net…which includes affordable colleges to,which they have a HIGH probability of acceptance.
Natl Junior Honor Society, I suspect. Middle school. Probably more regional.
My experience with my twins is that they’re a dime a dozen these days. About 20 years ago, there were special diaper & clothing programs, coupons, etc; people practically threw free things at them. Now you have to be at least a triplet to be “special” (plurality-wise) and it doesn’t get you much anyway…thanks to fertility drugs multiples are just very, very common.
The “advantage” I have with mine is that I have two in college at once for the entirety of their schooling, and they’re both at meet-100%-of-need schools, so I get that bump, which is offset by the cash flow pain. The overall advantage is that my need-based gift aid is up because I have more in school at once. We have high income and don’t qualify for aid at most schools, but because I have two, and at these particular schools, it ends up costing us less than if they’d gone to our expensive state flagship. Again, though, we’re paying for both at once. Thank goodness for the school payment plans. 
OP just needs to run the NPCs, this generic advice isn’t useful without numbers, a salary of a bit over 200K (@gibby) vs a bit more over 200K yields a big difference in EFC from even harvard for 3 in school, high earners usually have decent assets and that plays a part. OPs parents have been clear, they have probably already done their ground work. The OP needs realistic options for stats and COA.
To the question at hand, no, there are no sibling discounts for twins. I have twins beginning their sophomore years at two different colleges and their older sibling is starting his senior year. So, when all is said and done, I will have had two years of overlap with three in college and then two years with just the twins. All three plan to attend grad school and I plan to assist to some degree though they will carry more of the financial responsibility during their grad years.
Key strategy is full academic scholarships as we earn too much to qualify for any need-based aid. So, we have not paid a dime for tuition at any of the three universities. We cash flow all the rest (fees, room and board, books, travel, etc). Second helpful strategy is to get moved out of on-campus housing as soon as possible if there are good alternatives. Twins can share an apartment and had my twins attended the same school, they would have. They could have even shared a car rather than me needing to buy them each an economical vehicle.
As to dreams about the Ivy League, there is a world beyond the Ivies, and thank goodness for that. Focus on what you want to do with your life and then find the path that takes you there without enslaving your parents or yourself in debt. If a $200k household requires need-based aid at Harvard, that is a clue that the price may be too rich. It all comes down to a numbers game and once you and your parents are ready to sit together and have a frank discussion about money, you will come to understand the reality - which, frankly, is and will be better than any dream.
Best of luck.
There is a sibling discount at my daughter’s school. Each sibling gets $2500 off tuition while in school at the same time. Both (3? 4?) have to attend this school, not just be in any school.