To my knowledge, there aren't any high schools in Hillside Lake at all. I'm not even sure there are schools of any kind, with the closest being Van Wyck Junior High just off to the west in Fishkill Plains.
It's in the Wappingers Central School District as far as I'm aware, and I would imagine the closest high school to Hillside Lake is Roy C. Ketcham HS. I'd say that's about 10 minutes or so away. GreatSchools rates it as a 6/10 (based on its test scores) and local reviews give it three stars. From what I recall of Ketcham, it's pretty big and relatively clean, and they have a strong athletics program. Enrollment is a little high at about 2,000 students, with class sizes a little bit above New York State averages.
