slug should be unique for organizations
slug should be unique for organizations

BelieveC/classroom,hackerkid/classroom,mkcode/classroom,hackerkid/classroom,ConnorCartwright/classroom,BelieveC/classroom,mkcode/classroom,BelieveC/classroom,BelieveC/classroom,mkcode/classroom,ConnorCartwright/classroom,ConnorCartwright/classroom,jasnow/classroom,jasnow/classroom,hackerkid/classroom,jasnow/classroom