go to www.opalexplorenature.org and click on' kids zone' ~ you will see what children and their schools can get involved in~
a sample from the site below

Learn about the incredible lives of honeybees and butterflies and discover why a cockroach is one of the toughest creatures alive
Honeybees - Discover their secret lives

Cockroaches – why they are the world’s greatest survivors

Butterflies – Learn about their fascinating life-cycle

~ get them interested in bird watching,being able to identify them and putting food out to attract them to the garden , being able to identify trees etc~buy some seeds ,plant them and watch them grow ~ cress etc for
there's a whole world out there!~

if you have a spare small plot of garden let them have 'ownership', plant what they'd like and encourage them to look after them. Get unfussy plants that grow quickly.

Arlene has suggested some fantastic links too.

Try asking at their local school what they are doing in lessons and see if there are things you can do to support/enhance their school experience.

Children like to help and be involved so giving them a patch of their own where they can grow things along side yours. Involve them in the eating and cooking of what they grow. Also let them stay up sometimes to watch the nocturnal life in the garden such as hedgehogs. This all helps them understand nature and how to care for it.

Just picking up on the lives of honey bees thing above, if you can possibly interest children in beekeeping, for example being shown a hive by a local beekeeper (who can loan them protective equipment), a child will learn more about nature than from almost anything else.
I learnt far more about nature and plants from starting to keep bees than from anything else I ever did or read. That's because with bees you are constantly watching weather conditions, what is in flower for the pollen, whether the bees are flying or sulking in their hives, and whether they are being troubled by pests like wasps and hornets.
You also start watching all the other insects like dragon flies (which predate on bees) and hover flies and bumble bees to see which insects visit which flowers and in which weather conditions. So you also start learning the names of all the different wild and garden flowers, as well as all the flowering trees which provide nectar.
I'm so fanatical about the value of beekeeping that I'd make it a compulsory school subject if I could!

~ that would be such a good idea~ I know that some schools have a hive but no doubt you will get the old Health and Safety brigade causing problems~

elf n safety prevented my daughtes school having one as 3 parents put in formal complaints to the lea. lea came down on their side. :o(
I and a few others lobbied long and hard.

~everyone is scared witless of being sued these days~