It is perfectly normal to be experience muscular pain after classes. The pain is caused by sudden changes in physical activity and muscular loading and usually lasts for 3-7 days. As your body adapts to the training and becomes stronger and your conditioning increases, you will feel less and less discomfort after classes. This muscle soreness can be reduced with a thorough warm up and warm down before and after activity.
Remember, this pain signals that your body is adapting and getting stronger.