Help students to understand that American political life is, at least in theory, fundamentally egalitarian. Two of the last three presidents, Bill Clinton and Barack Obama, grew up in poverty, which means that anyone who can convince his fellow citizens to vote for him can become president. You can ask older students to discuss the issue; after all, if anyone can become president, discuss why the U.S. has never had a woman or a Jewish president.
If you are teaching during an election year, allow your students to participate in a mock candidates' debate. Let your students debate national, state or local political issues that interest them, or ask them to debate a school-related issue, such as how long recess should last or if pizza should be served for lunch everyday. For more fun, let them dress up as if they were appearing on an actual televised debate.
Another election year-related option is a straw poll or mock election. Even if they lack developed political ideas or convictions, students will enjoy the opportunity to express themselves and their opinions by voting. Many resources, such as Time Magazines's Time for Kids, are available that help children to understand international affairs and American political news. Holding mock elections also helps students to become enthusiastic about voting in actual elections when they become eligible to do so.
If you do not find yourself teaching during an election year, hold an election for class president and use this as an opportunity to educate students about the American election process. Allow students to organize themselves into two political parties and go through the process of nominating a candidate who will then represent them, along with a vice presidential candidate of their choosing, in the general election. You may also incorporate one or more debates into the class president election process.