I would like to ask, "How many kanji are you supposed to know?" My best guess was
（漢字を）何字知っているはずですか。 I omitted 漢字 since it was in context
This was reviewed by a native Japanese speaker and I had it corrected to 何字知っていますか with the explanation that the previous "is over complicated". However, I see no reason why the corrected sentence conveys the sense of "supposed" that I intended.
Could someone please verify that the previous question does indeed sound over complicated and perhaps provide a better way to ask that question (that conveys expectation rather than fact)?