These are just suggestions, which you can alter or combine, or you can create your own.
Here are some notices that have been used (edited slightly by us):
ARE YOU GAY, LESBIAN, Bi, NOT SURE, OR CURIOUS?

Write to [your group address], a student e-mail group
for our school only, and let’s talk about that.

Use an e-mail address that doesn’t reveal your
identity, and we’ll make sure you remain anonymous,
if you later decide to reveal your name to us.
SOMETHING NEW FOR OUR SCHOOL

Some of us have started an e-mail group,
for our school only, to get to know other gay,
bi, lesbian, wondering, and curious students.

If you fit into one of those categories, write to
[your group address] to get to know others like
you.  If you want to start out anonymously, use
an e-mail address that doesn’t show your name,
and is not listed in the Student Directory.
ARE YOU SOMETHING OTHER THAN TOTALLY STRAIGHT?

If you are a gay, bi, not-sure, or curious guy or girl, write to
[your group address] and get to know others like you.

We will protect your privacy, until you want to reveal who you
are, so use an email address that nobody else knows.
***************
***************