How can I make database normalization more clear?
There are some things you can only "get" by having repetition wear it into your brain.

This seems to me like a clear use case for first making them do it the hard way. So, construct a non-normalized schema and make them walk, painfully, through keeping everything in synch. Done right, they will be thoroughly sick of it after just a few updates.

Then, step by step introduce the normal forms, and look at how much easier updates are at each step.