✔ 最佳答案
That is very easy in the handling procedure.
You first report to School B first with the slip left there during the registration stage. If School A confirms to accept your application as new S.1 student, then you have to return School B for cancelling the registration, seeking the slip and use it to re-register in School A with the same steps. You can then be the authorized School A student.
Even the S.1 Attainment Test was over and you have been assigned one S.1 class by School B, the above procedures are still valid. You can still withdraw from it and transfer to School A at once. There is no need to inform E.D.B. as well.
Hope my explanation can help you.
參考: Mathematics Teacher Mr. Ip