In theory, the biggest immediate impact would be at Wando, where a significant portion of this year's junior class is Academy-affiliated. Where will those kids play next year? Who really knows? It's all speculation for now.
That said, Wando has over 30 kids on its current varsity roster, many of whom no doubt would do just fine at the high school level, if presented with more playing time and opportunity. Also, Wando's JV wins a significant majority of its games, including a recent JV tournament in Columbia, so there are numbers in underclassmen.
Would there be an impact? Obviously. Would that impact translate into a more level playing field? Arguably yes. Would that "level playing field" translate into fewer victories? Logically, yes. Though it's hard to quantify.