Practice doesn't make perfect; perfect practice makes perfect
One of the most effective methods of learning is by teaching. I would suggest giving your more experienced medics (whether they be basic or paramedics) certain skills stations or presentations to evaluate less seasoned members. Start out these lessons by stating the rules, "Everyone pays attention to the person speaking and nobody interrupt the presenter. If you have questions, raise your hand, and no questions are stupid." Evaluate these stations or presentations as an audience member. Should you see one of your presenters chiding or criticizing someone, ask them a difficult question related to the topic that you know they won't have the answer to (meaning for every lesson you should have a couple really difficult questions and answers prepared). This kind of puts everyone on a level playing field, because no matter how good you are, there's always something to improve on.