Little bear and punctuation

Little bear is now officially six and is basking in the glow of being able to spell things.  He also has a very mischievous sense of humour.  He will ask me things like, 'Mummy, how do you spell 'house'?'
I will pause and say, 'H-O-U-S-E.'
Little bear will grin and say, 'Correct!'

Today we hit the dreaded apostrophe.  'Mummy, how do you spell 'She'll'?'
I wrote the word down for him and explained that the apostrophe stood in for missing letters.  Little bear nodded and looked thoughtful.  'It's like a comma,' little bear said.  'How do you use a comma?'

I paused.  This was not something I was really ready for, and the use of a comma was not something I felt I could usefully help little bear with.  There are a number of reasons.

1.  I am not really sure how to use a comma myself.  I was never taught how at school, but I have picked up knowledge from usage and self help books.

2. I grossly over use the comma myself, when I write things I always have to go back and take out half the commas

3. I am not really sure of the usage that they are planning to teach in schools. 

4. I was pretty sure that this was part of stalling tactics as we were trying to get little bear ready and out for a visit to my brother. 

This is only the start.  I have a book called 'Maths for Mums and Dads' as they do it all differently now to the very basic stuff I can remember and I think I had better start reading it.  And some books on punctuation while I am at it.