From the SCHSL Constitution:

Before being considered as a member of the League, the non-public school must clearly define its attendance area
as one of the following: (1) the attendance area of the public school in whose attendance area the school is
located, (2) the school district in which the school is located, and (3) the county in which the school is located.

According to:
http://www.sciway.net/city/danielisland.html

Daniel Island is a large island located three miles north of Charleston Harbor, between the Cooper and Wando Rivers. It lies within Berkeley County but was recently annexed by the City of Charleston.

Which county can BE draw from, Berkeley or Charleston?