The three elements of a gift

Inland Revenue says there are three elements to a gift:
1    It has been made voluntarily.
2    It is by way of benefaction – the receiver gets some benefit out of the gift.
3    The donor doesn’t get a significant benefit in return.
One of IRD’s concerns is school donations. Donations made to a general school fund are real donations so long as they are not a substitution for fees. 
Similarly, a donation for a school trip is not seen as a donation because the student gets the benefit of the trip.