They went to college, journalism major. Big surprise there. They had to pay for it on their own, having had a nice student loan to pay off. Only Clark took longer, let's say a year, since he worked more to support them.
Just FYI, a bachelor's of journalism takes four years to complete assuming you graduate on time. And they would have done summer internships, too. I think Lois did hers at the Planet in the real canon.
