[brettlewis]

Try this out:

add_action( 'user_register', 'assign_membership_on_register', 10, 1 );
function assign_membership_on_register( $user_id ){
	$user_info = get_userdata( $user_id );
	$email = $user_info->user_email;
	$data = array(
		      'school1.edu' => array(
				'bp_id' => 2,
			),
		      'school2.edu' => array(
				'bp_id' => 3,
			)
		      );

	$output = substr(strrchr($email, "@"), 1);
	groups_accept_invite( $user_id, $data[$output]['bp_id'] );

}