Hi, I'm Carl Azuz, and you're watching CNN Student News. Today we're talking about political primaries, a matriculation milestone and a musical mentor. But we're beginning in the state of Ohio.

Residents and officials in the city of Chardon are trying to make sense of a shooting at a high school there. One student was killed in the attack; four others were wounded. According to reports, the suspected gunman is also a student at the school. He was arrested yesterday.

As students ran from the shooting, some of them used their cell phones to call police, or text their parents to let them know they were OK. A lot of schools practice what to do in these types of situations. They run drills for shootings or natural disasters. And one student at Chardon High said he thinks what happened yesterday could have been even worse if it wasn't for that preparation.

I think that's what really helped keep it at a minimum of what it was, as bad as it was already. I think it could have been a lot worse if it -- we didn't do the drills that we -- that they had us to do.

Jumping now to the presidential campaign trail, it's been a few weeks since the last Republican contest. But two states are taking over the political spotlight today, and those two states are Arizona and Michigan. Voters are heading to the polls there, casting their ballots for Republican presidential candidates.

Former Massachusetts Governor Mitt Romney, former Senator Rick Santorum, former House Speaker Newt Gingrich and U.S. Representative Ron Paul -- they're trying to win delegates in these primaries and caucuses. Win enough, and you get the party's nomination for president.

There are 59 delegates up for grabs today in Arizona and Michigan.

 One issue that comes up a lot during presidential campaigns is education. According to a new report from the U.S. Census Bureau, the country just marked an educational milestone. Has to do with how many Americans have a college degree.

 In March of last year, 30 percent of adults who are at least 25 years old had a degree. Back in 1998, it was less than 25 percent. The director of the Census Bureau called this, quote, "an important milestone," saying the more education people have, the more likely they are to have a job and earn more money.

According to another census report, workers with a bachelor's degree earned around $20,000 more on average than workers with a high school diploma.

Today's Shoutout goes out to Ms. McElroy's social studies classes at Hilton Head Christian Academy in Hilton Head, South Carolina.

Which of these places is divided by the 38th parallel? Is it the Bering Strait, Korean Peninsula, Aleutian Islands or Marianas Trench? You've got three seconds, go.

The parallel at 38 degrees north latitude divides North and South Korea. That's your answer, and that's your Shoutout.

When those countries fought against each other in the Korean War, the United States was on the side of the South. And the United States and South Korea are still allies. They're both the target of harsh words from North Korea right now.

That is because of military drills, like the ones you see right here. The U.S. and South Korea are running joint operations right now . They're working together. But North Korea says the drills are designed to provoke them. And officials from the north say they're ready to fight a war against South Korea and the U.S.

North Korea's relationships with other countries have been uncertain since long-time leader Kim Jong-il died in December.

 Well, part of the tension surrounding North Korea has to do with its nuclear program. Similar situation in Iran. You've heard us talk about sanctions, penalties put on Iran by the U.S. and the United Nations. The goal of those sanctions was to get Iran to stop its nuclear activities. Matthew Chance has more on the tension between Iran and the integrity community.

 But Iran says very clearly that it is not building a nuclear bomb. It says that it's never done any research into building a nuclear bomb. It says that all of its nuclear activities are directed towards purely peaceful purposes.

The trouble is that it's, you know, not many people in the international community believe Iran. They do believe -- and there's evidence to suggest that, in the past, they may have conducted some research which would be relevant to making a nuclear bomb.

What we know is that it certainly doesn't have a nuclear weapon. I mean, that's one thing to make absolutely clear. What it does have is the ability to enrich uranium. Uranium is the substance which is needed to fuel nuclear reactors. And if you enrich it even more, it's the substance that you need to create a nuclear bomb.

Iran has been enriching this uranium for years now, as it has every right to do, because it's a member of the Nuclear Non-proliferation Treaty. It's allowed, under that treaty, to enrich uranium. But the trouble is, in the past, it's not disclosed some of its activities to the international community, and that's why there's such a lack of trust with Iran at the moment.

Well, IAEA is the U.N.'s nuclear watchdog agency. It's the independent body, which has, you know, a whole range of nations that are members, including Iran, that inspects nuclear facilities, not just in Iran, but all over the world.

There are a lot of questions that the IAEA has that Iran has not answered. For instance, it wants access, the U.N. does, to search suspicious nuclear sites that it suspects may have been the location where nuclear weapons testing may have been carried out or development for those weapons may have been carried out. And so there are lots of areas, lots of gaps in Iran’s story, that it has yet to fill out.