A blackboard in a classroom indicates you have a spiritual leadership ability to work with groups and help them to expand their consciousness to take them out of the dark. Spiritual leadership works through empowering others to achieve for themselves, rather than doing something for them. It also indicates another ability which works in combination with your leadership. You also have the ability to project your mind so that when you are engaged with others, they connect completely with what you are saying. It is like you are putting your hands inside their heads and rearranging their thought process.