As a Voluntary Pre-kindergarten teacher a lot of it is what the goverment tell you what you have to teach. It took me 3 years to get permission to plant vegetables with the kids in my class. I kept going to the owners with plans and reports how it would benifit the children. And putting the burden of the cost on my self. The reason I do the things like container gardening with children at 4 and 5 is because they can take that knowledge with them. They are each getting a book of pictures telling about what they planted and how it grew. And the different stages the plants are in.
People have told me it's a waste of my time doing this. But I think I am teaching something they can take with them. To see city kids get excited to see what they are growing is a blessing to me and it is also rewarding.
That experience could prove to be priceless, someone must show them. I don't think your effort is in vain. Just think about all of your memories growing up. These will be carried with them!
Then you would of got a kick out of the children in my class today when I was changing the hinges on a cabinet door that wouldn't close. They were suppose to be playing in centers. Lets just say I drew a crowd full of questions wanting to help me instead of playing.