I like to give them a variety of materials and then have them sort them into magnetic and non magnetic.
It is also fun to teach them about poles.
Like poles attract and unlike poles repel.
The lessons include:
What items attract to a magnet?
Attracting and Repelling North and South Pole
Reading Informational Text Lesson (With a three page article)
Creating an Electromagnet
Making a Temporary Magnet
Will a magnet attract through other materials?
Exploring Sand with Magnets
Push and Pull With Magnets