I created a new GPO and linked it to Teachers. As in the article, I set the GP to Preference mode for Internet Explorer Maintenance. Then I sorted out the settings. Although you still don't seem to be able to see the settings in the normal settings window for the GPO, they seemed to be set OK.
I logged in as a teacher. Checked that the settings were applied in IE Tools Options Advanced. However, when I opened IE, my home page didn't appear. Closed IE and tried again. Then it did appear. Closed IE again. Opened IE. Then I got a Microsoft update page as the home page. Then the home page disappeared again. I logged out and in again. Same thing. Tried another user group to see if IE was playing up generally, but that was fine. Removed the new GPO and all back to normal.