What is the credibility of the GLSEN?

I got accepted to the 2011 Safe Schools Advocacy Summit, but in order to let me go my mom wants to know more about the credibility of the organization, which makes sense. However, and links or whatever I can get would be fantastic. This is a once in a lifetime opportunity that I am risking missing out on.|||We take it your not from the UK then P%26amp;P :-)