I've started working at St Chrysostom's Primary in Ardwick. When I asked a group what they'd most like to grow, one boy said "avocados!"
We were gathering ideas so I didn't want to curb his enthusiasm by telling him that we couldn't or that it would be difficult and, besides, something made me think that you could do something with avocado stones. When I looked it up in my old House Plant Expert book, there it is on page 150: Fun Plants.
Apparently you put the stone in a pot, keep it warm and dark until it germinates and then you can get quite a nice plant (no fruit though). There was also mention of other seeds that might produce a plant including citrus fruits, dates and, crucially, pomegranate because today at St John's one girl said she'd love to grow them. So, we'll have a go and report back.