Let's see. First year was their freshman year. So second year was their sophomore year. Anyone know if the school they go to is one of those schools in which there're 3 or 4 grade levels? If it's the 3 grade level kind (10-12) then in the 3rd season they'd be Seniors, and Clark's probably about 18 (Which means he started out around 16). It it's a 4 year deal (9-12th), then Clark's at best 17. Which is ok. Clark's an alien, after all. He can look a little bit older. At least the rest look younger, especially Pete.
Hopefully, though, this third year will be their senior year, and they'll be out of high school after this season.
As for Lois Lane, no, she hasn't appeared, yet. What I've heard, however, is that she's a cousin of Chloe. Not particularly fond of that idea, however, or the idea of making her a couple years older than Clark. She's supposed to be in college, already. Maybe it's just me, but I don't like the idea of Lois being about Lex's age.