- Special needs students. This could be a really active community for you.
- Arts/Music/Theater programs and participation rates.
- Innovative educational programs. One of the HS I attended had an on-campus fish hatchery that was almost entirely student run, it also had a professional choral program--as in, students in the "varsity chorus" got paid professional rates for a summer show series. Another that I attended had a pretty unique combined history/literature and later math/science program. I could imagine parents being interested in finding those kinds of things.
- University affiliation. Many colleges/universities are affiliated with K-12 schools where they are involved in applying the latest in educational practices.
- Early college programs. My wife managed to get her first 3 semesters of her Mech-E degree paid for through an innovative relationship between her HS and the local Community College. The local CC also has a great direct-to-university relationship (all credits transfer) with two local Universities. Allowed her to graduate undergrad a year early and with half the student loans she otherwise would have.
- Proximity to cultural institutions. Friends Select in Philadelphia is located on the Ben Franklin Parkway... walking distance to the Franklin Institute, Academy of Natural Sciences, Phila Art Museum, Barnes Foundation, Rodin Museum... It's almost embarrassing.
Standardized test scores are important, but they aren't necessarily the only thing parents are looking for.