Hey i found this online from a GMAT instructor. I Hope that this is going to help you.
in the context of the gmat, i would generally choose plain old except, because it's more concise. i'm not sure i've ever seen a formal pronouncement on the issue, though.
there are some instances in which except must be followed by some preposition, in order to properly introduce some clause - but even in most of those cases, there's a better preposition than for. here's one example:
not as good: he was the perfect employee in every way except for that he always showed up late.
better: he was the perfect employee in every way except in that he always showed up late.
except 和 except for 的区别
在于
except for 后面的名词和主句的主语不是同类事物；
except 后面的名词则是同类事物
然而在GMAT中，一般不区别except 和except for，两者可以等同。
except 的考点应该只是except 和excepting的区别：
excepting在GMAT 中只能用于否定句之后。
例如：
everyone helped，not excepting him。
all were there，not excepting them.
everyone, not excepting myself, must share the blame.
OG 12 V-18
18.Except for a concert performance that the composer himself staged in 1911，Scott Joplin's ragtime opera＂Treemonisha＂was not produced until 1972，sixty-one years after its completion．
(A) Except for a concert performance that the composer himself staged
(B) Except for a concert performance with the composer himself staging it
(C) Besides a concert performance being staged by the composer himself
(D) Excepting a concert performance that the composer himself staged.（A）
(E) With the exception of a concert performance with the staging done by the composer himself
2. GWD17-Q12:
Mauritius was a British colony for almost 200 years, excepting for the domains of administration and teaching, the English language was never really spoken on the island.
A excepting for
B except in
C but except in
D but excepting for
E with the exception of(C)
首先，句子中需要一个转折，因此用BUT,
其次，C D中的except in 的后面的domain 搭配
