"In that"

Consider the following sentences, both of which are grammatically correct:

1). The class succeeded in that they earned high marks.
2). The class succeeded because they earned high marks.

Sentence (1) says the class succeeded, but we're limiting our definition of success to earning high marks. The sentence intimates that the class was actually unsuccessful in other ways (maybe they forgot the material after they took the test, maybe they didn't learn the social skills they were supposed to, etc.). "In that they earned high marks" modifies "succeeded" here, and "in that" means we are limiting the way they succeeded to this one particular area.

Sentence (2) says that the class earned high marks, and that caused them to be successful later on in life (they all got good jobs as a result of their high marks, etc.) - it's an OK sentence but probably not the meaning we intended.