This might be useful to folks. If you want to calculate your son's Academic Index for the Ivies (176 is the absolute floor, BTW), here's a roughly accurate way to do it:
(1) ACT score x 2.23, plus (2) Unweighted GPA x 20, plus (3) the average of his SAT subject tests divided by 10.
So if, for example, your son has an unweighted GPA of 3.4, got a 29 on the ACT, and got a 550 and 590 on two SAT subject tests, his Academic Index would be: 65 + 68 + 57 = 190
As with all things academic, the higher the better.