In my ongoing battle to standardize our environment, I went to one of our schools to
reset the admin password on all of the computers. I sent the below command using
apple remote desktop’s unix command section.
passwd admin Secretpassword Secretpassword
I put the password twice because you have to confirm the new password. You could
substitute any local account for admin and reset it’s password as well.
Of course, all of this assumes you know a current account that has access to run
commands through remote desktop on all of computers.