I see the benefits to this, especially in the event of a disaster or school shooting...but to not advise the parents? Dumb.
http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2005/02/10/BAGG0B8I4D1.DTLSutter, Sutter County -- Angry parents, saying their children's privacy rights are being violated, have asked the board of the tiny Brittan School District to rescind a requirement that all students wear badges that monitor their whereabouts on campus using radio signals.