Prepare the soil for your ants. You want the soil to be loose enough for them to tunnel but not so loose that the tunnel collapses. try mixing 2 parts clay with 1 part sand if you don't have a comparable soil nearby. You can collect soil from your garden or alternatively use a little bit of potting mix and some sand from the gardening store.
Collecting soil from the garden
When looking after your ants you can use a water spray (atomizer) to keep the soil a little bit moist... but don't drown them!
Place a small jar inside a larger jar. This creates a small gap where the ants will burrow through the soil and allow you to see their intricate tunnels.
Pour the soil mixture into the gap between the two jars. If you want you could alternate soil textures to demonstrate different soil horizons as well as to create an avenue for variable testing.
Some different soil horizon models being used for the ant farms
When you add your ants to your ant farm make sure that the lid is secured so they can't get out. You should tiny holes in the lid to allow oxygen into the container.
Don't forget to feed your ants! They love pieces of fruit as the fruit contains a variety of sugars that they need to grow. Just be sure to only give small amounts of fruit or you could introduce mould into your ant farm (if not everything is being eaten you're feeding the ants too much food). Don't be tempted to give them meat as rotten meat is a health hazard and could bring other pests into your ant farm.
Cut apple slices for the ants to eat
Finally, cover your ant farm with a cloth to simulate the darkness of being underground. This will mean that they will more likely burrow near the sides of the container. Also, keep the ants in a warm location but out of direct sunlight (the container will heat up too much otherwise).
Take regular observations of the ant farm tunnels as the days progress. This might be a great time to write a student blog!
At the end of your experiment please release the ants back where you found them (no need for them to die!).