This was the written advice given by a particular teacher.
At first, I was quite surprised that see this, rather than the advice that they should see their teacher first.
However (and I have done A-level maths myself many years ago), the more I think about it, the more I see some logic behind it: trying to understand something with one's peers is a step towards the independent learning that's needed for A-level maths (rather than GCSE or lower), and certainly for university work, where independent studying is essential in many subjects.
Does this seem right to you? Sometimes you hear of A-level students really struggling, because they're used to being "spoon-fed" everything; and suddenly they have to solve problems more independently.