Phoebe Terese: I might have made a mistake about that lizard. And I might have made a mistake about that jackrabbit. And I might have even made a mistake about that tortoise, but there's one thing I know I'm not wrong about.
Arnold: How much you wish you'd stayed home today?
Arnold: I knew I should've stayed home today.
Phoebe Terese: C'mon, Arnold, let him go. It's just an egg.
Arnold: But it's Dr. Skeledon's egg. And it's up to me to get it back to her.
Phoebe Terese: Gee, what a guy.
Keesha Franklin: It must be cold down there because Saturn's pretty far away from the sun.
Tim: But Ms. Frizzle said "cold and dark."
Janet: It could be very, very dark on Saturn.
Carlos Ramon: Oh, no you don't! You just want to grab more stuff.
Janet: Hey, I'm just trying to help! If you want to play "Let's Find Ms. Frizzle Without A Map" for the rest of your life, that's fine with me.
Answer: In general, quite accurate as that was the point of the show. To teach kids about science. As the show is now over 20 years old, some facts have changed as we're always discovering new things. For the time, it was as accurate as it could and much of it is still accurate now.
One thing I think the show gets wrong is the idea that electrons stop moving when you break a circuit. Electrons never stop moving.