My SIL told me that she was more busy once her two girls were in school. Organising them, drop offs and pick ups, helping them with homework etc and getting involved with school activities. And of course still had to run the household.
I think its important to be there. A part time job within school hours isnt easy to find but would be ideal.
I think a sahm role is just as important and valid as going out and working for a wage. Some of the responses in this thread are just mean.