I was wondering which of the three tenses is the most suitable to refer to a previous action, which recurred on multiple occasions, as in the following example:
I usually have to read over what has been taught/had been taught/ was taught in the class.
I'd use the simple past if there was a specific time reference in the sentence like "..what was taught on that day" but I'm not sure if present perfect or past perfect would work in the sentence as it is?
I think that you'll be fine with any of the three in terms of clarity of meaning, though I'll discourage the past perfect in this case.
To my eye the issue seems more grounded in the first clause of the sentence: I usually have to read over, which establishes that the speaker engages in this behavior exclusively in the present (if not on a regular, ongoing basis). I think that present perfect and simple past are both appropriate here.
The relevance of the material that was taught is still in effect at the time of any given review, so the past perfect seems undesirable to me. It is also the case that the past perfect suggests that the pattern is not ongoing, which is at odds with the first clause's suggestion of an activity that still occurs. Such a reading would suggest that the speaker regularly reviews things taught in a specific period of the past, such as reviewing his/her own course notes from a specific class taken years ago, repeatedly. Conjugation in the second clause aside, I would not find this to be a natural reading of the sentence as constructed.
As for the other two options, with no context beyond what was presented in the OP I think that they are functionally interchangeable. Presumably each "unit" of teaching is what is being reviewed, whether that's by topic, course, day, semester, individual lecture or whatever. Each review is paired with some amount of teaching, but that the groupings are appropriate is implied by the larger sentence.
So, whatever unit is being considered, that material definitively was taught in the past-- presumably the speaker would not be reviewing planned material for an upcoming lesson at the same time as reviewing material actually delivered (if this is the intended meaning, the sentence itself does not suggest so). At the same time, it remains the case in the present that that material has been taught, and the review of that past action implies that that action is still relevant at the time of review.
TL;DR: My read of the sentence favors the simple past, as each "unit" of teaching is discrete and occurred only in the past with regard to any given review, and its relevance to the present exists only within the context of the review itself. The present perfect is also technically correct and appropriate but adds no useful information beyond what the simple past supplies. Past perfect may not be appropriate because it suggests a different meaning than the other two options suggest, leading me to believe that this is not the intended meaning.
To tighten up the sentence, you would probably want to rewrite "what was taught in the class" anyway, because it's passive voice.
For examples, including a few variations on how to define what was taught:
"I usually have to reread my lecture notes."
"For Chemistry 101, I usually have to reread my notes after I attend a lecture."
To make this a past tense, you might say,
"When I was in Chemistry 101, I usually had to reread my notes to understand its lectures."
The multiple recurrences you wanted to highlight in your choice of tense are still contained in the word "usually".
