. How might knowing the parents expectation help you to understand your students?

Families suffer from an interesting effect called the "Narcissism of small differences" which often informs the relationship between parents and children profoundly.

That means that often a child will want to be like their parent, but only to a certain point. Families are normally very alike, but they exaggerate small differences as a result of being too similar.

A parent is normally not informed neessarily by what is actually best for their child but what is best for their "idea of their child", who is often more a projection of their own wishes than who and what the child actually is.

You can't tell the parents this directly because they don't want to hear it, it's somewhat insulting to have someone telling them about their own child after all. On such occasions point out strengths that the child has that they might not have noticed in their own assessment of th child's personality and competences, play down negative information or lead the parents through a logical path to a conclusion you wish them to reach without ever telling them what you expect.

Finally this may not be necessary. If a parent's assessment of their child tallies well with your assessment of their performance and personality you may be happily on the same page and no special care needs to be taken.