How do I bypass the preferences set in WGM on a client machine logged in as a local administrator?

I'm trying to sort out WGM control over 21 macs after a failure of the xserve. I have added the machined to WGM and set pref. However when I log into the client machines as a local administrator I cannot accesss system pref fully. I seem to remember there is a way to bypass WGM pref for admins by pressing teh Option key when logging in? However this no longer works?

Anyone have any ideas?

Surely I don't have to remove the mchine from the WGM group evertime I want to administer a client machine??😐