See the classroom and the students sitting in it - to a parent meeting.
To dream that you are in class, is a metaphor that you need to have more class.
To dream that you forget to attend a class you signed up for, indicates your anxieties and fear of failing. You may also be lacking self-confidence in your ability to handle new responsibilities or projects.
Being in class, as in a school, can represent:
Learning or being taught
Self-improvement, personal growth or evolution
Life lessons or learning through experience
Anything else you associate with a classroom situation, such as boredom, interesting topics, friendships, fun, getting into trouble, punishment, teachers or authority figures
Your actual school classes
The era of your life when you went to the school that appears in your dream, or a relationship, thoughts, feelings, experiences, or unfinished business from that era
To be in it - get severe reprimand from his superiors.