To dream of a chalkboard symbolizes problems you may have encountered during your childhood and youth. Pay attention to the message that is being conveyed here. Perhaps you need to prove yourself worthy or capable of handling a certain issue or situation. Take note of any words that are present on the chalkboard. This dream may also represent obligations or responsibilities that are in arrears.
To dream that you are in a classroom indicates that you will experience a significant event or occurrence that will have a huge influence on your future decisions.
To dream that you are giving a lecture indicates that people around you find you devoid of fresh ideas - you are boring and uninteresting. Perhaps you need to work on enhancing your interpersonal skills. Alternatively, this dream may be a spillover of your rational, objective self.