All SCISA schools would play Single A in SCHSL. Porter-Gaud has the largest high school in SCISA with about 375 students. Pinewood has about 275 high school students. Cardinal Newman, Hammond and Heathwood Hall have high school enrollments somewhere in between. For comparison, SCHSL Single A schools Christ Church and Southside Christian each have about 300 high school students. SCHSL AA schools Bishop England and Academic Magnet have approximately 800 and 575 students respectively.
Comparing SCISA schools to Wando or Irmo or Lexington is as silly as comparing Christ Church or Academic Magnet to Wando or Irmo or Lexington. Anytime a SCHSL AAAA team plays a SCISA team and doesn't win by at least 2 goals, the SCHSL team has either played very poorly or just isn't very good at all.