Who told you about this? Can you see there's parent who accepted offer from a Dss and then received offer from another DSS? I don't think there's such 通報。
yw 響kln,ec 響tko,兩間既收生標準又唔同,先天性就已經決定佢地重疊既人唔多。用yw諗,考到既150人,會有幾多去tko考﹖掉轉,考到ec既150人,會有幾多考出kln﹖再講,yw有一半人唔會去考ec,因為女仔,假設中左ec既男仔(假設75人)都考yw,呢75人撈埋入yw2500人入面,會有幾多個中呢﹖計機會率,同時中ec 75/750(減去一半當女仔),又同時中yw150/2500係幾多呢﹖當然,考起上黎個機會根本唔係平均,因為唔係抽籤,越叻仔梗係越大lar。祝好運!