The difference between 'X's Y' and 'Y of X'.

[peppy_man]

(1) private school's school fees

(2) school fees of private schools

My teacher recommends (1).
Not just about these two sentences, she prefers 's.
I' d like to know exactly what is the difference between the two.
Also I'm intereted in which is more formal or which is more useful.

Thank you.

[Tdol]

The first is more common. The second is more formal.