Anyone working for a HigherED, K12, or a support District can join.
You do not have to be a Security Researcher, the consortium aims to include and educate, not gatekeep.
Any member can use the Invite Module built into the web application to invite and include their co-workers and peers.
The invite email contains a link with a one-time-use token. It'll allow you to create an account and upon creation, expire.
If you don't see an invite after someone says they sent it, please check your spam folder.
Chances are that someone in your network is a member so ask around.
If no one is, feel free to email firstname.lastname@example.org for a review of your employer and an invitation.