I am also surprised that your son did not get it. Generally a 33 ACT with a top 10% class ranking (I assume your son was top 10% if GPA was nearly perfect with all honors and AP classes), a good bit of EC activities and solid essays should have gotten in. As for your younger son, I am not sure if the summer immersion classes would necessarily help with the application chances. My advice would be to put work into getting the essays really strong if your son already has good GPA, ECs, and hopefully an ACT of 30+ the 2nd time would be the charm.