I don't recall when they made it mandatory for your kids to have a number. It may have been sometime in the 70's. I kind of remember thinking it was a ploy for big brother to track you from cradle to grave, just can't place the year.
Sports teams often ask for Social Security numbers. Davidson says that this is a common source for child identity theft.
Child-care programs, too, require detailed identity information about kids in their care.
Interesting Article!
http://www.fool.com/news/commentary/2006/commentary06011001.htm
I don't think it is mandatory. I got mine in the 9th grade. Our social studies teacher said it was time. We were young and dumb and just filled out the forms. I have read some anti-tax info that says the original law stands that you do not have to have a SS# to work. The problem is finding someone to hire you without one. lol