You have a great start. I would add something about the kinds of food they eat. Stuff that kids would have in their lunch bag like apple cores and banana skins but not ham or potato chips.
Make up some flash cards of food pictures off the internet and test the class as a whole. Hold up a card and ask, Is this good for worms to eat?
Teach them how to separate the worms, they like that.
Talk about how much they eat per day. Ask them how much they weight and tell them how much they would have to eat if they were a big worm.

All very good ideas.

Be sure to point out that they eat paper.
Telling them that they really eat the microbes feeding on the paper could go over well.

Always a great forum to help with ideas. Thank you everyone for the great ideas

The talk turned out to be very interesting. My daughter was extremely proud. Many children (and teachers) would not touch a worm, whilst other wanted to take some home. Children asked many questions, to which many answers were promptly offered by their friends. The teachers afterwards asked lots and lots of questions, and wanted to know more about vermicomposting. In order to promote vermicomposting, I was thinking of making a bin for the school, and so hopefully get some parents interested. I am also thinking of compiling something on vermicomposting. Maybe a how-to pamphlet, or maybe something about vermicomposting and wastemanagement.

The Waikiki Worm Company in Hawaii does in-school worm workshops. You might take a look at their website and get a few ideas. Their mini-bins look like a good hands-on introduction to vermiculture: http://www.waikikiworm.com/6wwschool.html

Here is a link that might be useful: Waikiki Worm Company

Check out the home made worm harvester in the "School Worms" section.

It is very simple and look very easy to make.

Thank you everybody. After finding a company over here with similar objectives to that of Waikiki Worm Factory, I'm now considering buying a can-of-worms for the preschool.

I taught three kindergarten classes about vermicomposting at the private schools request. As a Master Gardener who loves worms and children I jumped at the chance. I brought a homemade bin for each class and worms. I gave a list to the teachers to send home to their kids to bring(garbage and papers of course)
We used a marker to divide the bin in quarters. They would fill each quarter then when the fourth was full the first should be ready. It was half way through the school year so NO way would they filla can o worms. They were all sooooo excited . I was given a cute worm Thank you with all their names and a Great worm book I had admired in one class room.
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