A lot of schools outside London are seriously underfunded. In the Primary School where I worked, a lot of cakes and sweets were brought in for staff to share at Christmas and end of term. It was far too much. The PTA was always trying to raise funds for children to join the trips and outings, whose parents could not afford to pay. So a suggestion was made, definitely voluntary, for parents who could and wanted to, to make a small financial contribution. The last year I was at that school, no school trip was made, as coach companies had pushed prices out of reach, it was more profitable to take corporate parties than school children. There definitely was no obligation or chasing up of contributions.