Write in the present tense in the report?
How should one do this, since a report is in the past tense? For example, if I write about "the effects of online bullying," how should one write this sentence in the past tense: "This could lead to school anxiety" or "You'll get worse grades."
Since a further feature of the report, in addition to the use of the correct time, is also a neutral, objective reporting, avoid the use of the conjunctive.
Now on your questions, how the two sentences can best be formulated in preteriority:
a1) the (possible/individual) occurrence of school fears
or (if you are not sure that it is)
a2) there was the possibility that school fears occurred
b1) poorer notes were written
b2) This has written worse notes
b3) Students wrote worse notes