for your question:

儿子要学Accounting,是任何学校都行,还是必须Accredited School?
--I sugguest he goes to Accredited School.

需要读一个 Bachelor 学位吗？
挺需要的。

直到成为 Accounting，大约需要多少年？
I assume you wanted to say "直到成为 Accountant，not accounting".
--0yr-never after he graduates.

成绩水平有最低要求吗？
--no any requirements if he gets C/C above. of course,the higher, the better.

谢谢！
-- you are very welcome!