There are no laws regarding taking pictures of children.. there are no laws regarding putting pictures on the internet. Anyone can take a pic of anyone elses kids and publish them online
On private property its up to the person who owns/in charge to make up there own rules re who can take photographs.. to this end such as schools will do the permission thing before letting anyone take pics.
You should all be aware that in public anyone can take any pics of you or your children and do what they want with them.. there are some restrictions re commercial use but only if you or your child is the prominant feature of the pic.
My own personal opnion is that there should be laws.... But I seem to be in the minority on that one amongst photographers
