One of the more confusing facets of learning English is figuring out what the right words mean and what not. This can be a pain for anyone trying to learn the lingo, especially if you're not in the business of learning the language. The best way to avoid the pitfalls is to learn the lexicon. A good place to start is with a few simple vocabulary exercises that focus on the nuances of the twelfth grade Common Core. In a nutshell, the twelfth grade Common Core is an organized set of lessons and tests designed to prepare students for the high school equivalency test, which is often called the GED or General Educational Development examination in the United States.