Paper knob switches worked all right with copper tape circuits. But by no means would they earn a Six Sigma award. The performance of brass fastener switches (which you'll see in an upcoming Instructable) was also spotty.

I then wound up at the highlowtech.org site and saw their pull tab switches. These look simpler and perform better than other switches. A student can make one of these in minutes and spend the rest of the time investigating circuitry.

Step 1: Tools and Materials

Craft knife (Unfortunately. The rest of the project only requires five-year-old motor skills. If you don't want students to learn knife skills, yet, do some pre-cutting.)
A pair of scissors can also help
Card stock or index card
Copper Tape (Available as Slug and Snail tape at hardware and garden stores and home centers)
LED
3V battery

Step 2: Cut Some Tape

I cut eight quarter inch lengths from the end. You might need more or less.

Step 3: Layout Circuit

Leave gaps for the three components: battery, led, and switch.

Step 4: Cut Two Slots

Cut two 1/4-inch long slots above and below the bottom two lengths of the tape.

Step 5: Add Copper Tape

Add copper tape to your paper slip so that it will make contact in the upper side of the paper.

Step 6: Tape Battery and LED

Use a little bit more copper tape to secure the leads on your other components.

Step 7: Mark Your Tab

Write on and off symbols where the paper slip does and doesn't make contact with the bottom lengths of copper tape.

Step 8: Test Your Circuit

Make sure the polarity of the battery and LED match. The positive end of the battery should be connected to the positive (long lead) end of the LED. Check battery and LED and contacts if LED still doesn't light.