To see in your dreams writing in white chalk on a blackboard, denotes ill tidings of some person prostrated with some severe malady, or your financial security will be swayed by the panicky condition of commerce. ... Ten Thousand Dream Interpretation
Vision: Writing on a blackboard: start managing your money better and don’t borrow any right now.
A blank blackboard: expect to receive a note—and pay careful attention to what is says! Wiping a blackboard clean: you have thought through your new approach to a project much better than before.
Depth Psychology: Are you looking at a blackboard for help and advice? Is the advice a warning to watch out for losses and risks? Is it a reminder from your unconscious to prepare a certain matter more carefully? You will know the answer better than anyone else.... Dreamers Dictionary