Question: Teachers restricting the student’s curriculum before the exams. Is this permitted or is it haram?
Answer: This is cheating, it is not allowed for the teachers to do this. It is obligatory for the teacher to hide the exam from the students. The entire curriculum should be a possibility [to be tested on] in order that they [the students] should review all of it. The teachers should not restrict this for them because it is cheating on the exam.
[Taken from: https://www.alfawzan.af.org.sa/node/15215]
Faisal ibn Abdul Qaadir ibn Hassan