Harvest (in a tin)

We've just received the latest newsletter from my son's school which, among things, gives details of the annual 'harvest festival'. Now, when I was at school, a harvest festival was, as its name suggests, all about the harvest, i.e. fresh vegetables and things that people had grown. I can still see the school stage festooned in carrots, cabbages, lettuce, giant marrows and potatoes.
How ridiculous, it seems to me, is the instruction to all parents that NO fresh produce is to be donated and that food items must be either tinned or in packets, and to assist, the school have provided a list of 'acceptable' food items;

Why on Earth aren't they contacting the local supermarkets who routinely dispose of anything dented or past its sell-by date? Surely this would be be a better idea rather than expecting those who can barely afford to feed themselves to empty their larders. Is it any wonder our children have no idea where our food comes from...?