G. Mark’s Answer
You don't need any particular level of education to be a successful actor. However, you'll find that most successful actors have trained in some skills. It may be that these skills are acting-related, or training in various forms of acting and stage play. All of the actors I've known have had life experiences in other areas than acting itself. In my own personal opinion, these people have shown that they are able to convey some personal experience and feeling to their performances. So, like many other aspects of life, you can just get into an occupation and possibly succeed, but you have to realize that you are competing against other people who have gone the "extra mile" and tried to learn from others who have excelled in that particular field. And acting is no different. If you look through the biographies of many talented actors, you'll see a plethora of impressive backgrounds not really related to acting. Keep in mind that the value of a truly great performance is its ability to get the audience to relate to emotional experience. Knowledge of what those experiences actually are is what gives many performances their power.