You are certainly right about that growth and demographics of said population expansion (and there is a lot more to come). All this will lead up to some very lively discussions I'm sure about zoning, and configuration of schools once the doors open (or before).Actually it has already started.
From what I understand, the original (current) plan was to move all area middle school kids to the new school (that will sit on Clements Ferry Road - 41 end) and reserve Daniel Island School / Cainhoy School for elementary aged grades. This is similar set up to our neighbors on 41 (MP) with Pinckney/Cario/Wando progression. This of course means DI families will need to ferry their kids a few miles down CF Rd. which is being widened to 4 lanes to support the increased traffic. However there are scores of people who would prefer to split enrolment by location, rather than grade which would mean rezoning again to move more off DI School and out to Cainhoy for elementary ages and that would certainly affect the diversity and demographics of the schools. What we have in our neck of the woods is existing rural, largely African American communities bumping into urban growth and opportunities to tackle it in a number of ways. Will be interesting to see how this pans out.
It is a big deal as there are hoards of public elementary/middle school aged kids aging quickly on DI and (to a less degree) Clements Ferry. This new High School will have a very healthy feeder system. Class sizes at DI School in 6th and 7th grades are much larger than 8th and even more behind that based upon the largely young family crowd who live here, plus older aged kids already entrenched in private settings by the time DI School opened.
In any case, you are correct with what this will mean to school attendance (elsewhere). Clearly Hannahan will receive fewer (none) from East Cooper (that's the point), and I suspect over time many of those playing the county line game (attending School of Arts, Wando, and Academic Magnet) may rethink that neccessity and sell their postage sized patches of Charleston County land. I also think it will reduce the flow of DI School kids over time to Porter Gaud and Bishop England by a few heads. I know we are just looking forward to another option for our family and from a soccer standpoint, I'm excited as this area is pretty rich with good players and at least 3 quality clubs supporting them. This new school has the potential to play beyond its size (when it comes).