Science: Fair testing the strength of magnets

In Science today, Year 3 began their lesson by asking questions about magnets, including, "what would happen if we put all the magnets together?", "does it matter how old the magnet is?", "will the ring magnet be the strongest even if it is the smallest?", "which magnet is the strongest?". We discussed what we would need to conduct a fair test, including changing the magnet each time, but keeping the metal paperclip and method of measurement the same. After an interesting discussion about our predictions - some pupils thought that the size of the whole magnet didn't matter (because, in the case of the horseshoe magnet, most of it is made of plastic), but rather the size of the physical magnet was more important - we carried out our fair test before finally recording our data in a bar chart.