I am 25% Mexican and 25% Syrian. The other 50% I am European (Irish, English, hodgepodge.) Does my Mexican and Syrian ethnicity aid me in admissions to schools like Exeter, Andover, and SPS? If yes, how much would you say it helps? Thanks.
The Mexican fraction enables you to check the hispanic box.
Unless you hold syrian dual nationality, it counts for zip.
I would be cautious about checking boxes claiming to be a disadvantaged and/or URM being 25% of something. Remember they will meet you, see what school you attend, where you live and your family finances if you apply for FA. If you are trying to leverage something that is essentially trying to game the system it will hurt you, not help you.