You may want to check out 'Rule 5' though - as far as I'm aware, the only exceptions to the 500' rule with regards to take-off and landing must be under the circumstances that the manoeuvre is carried out at a 'Government, Authority or Licensed aerodrome'... not a school playing field.
That would preclude most private strips and many beaches.
I'm assuming 'sports field' isn't your average football pitch (if nit is, he'll need a helicopter). I've taken off from Hough End playing fields in Manchester in a 172 - but that is quite a big area of land and was an airfield a long time ago (but it may have been bigger back then).
SSD