Explain that a star's apparent brightness from Earth depends on both its true brightness and its distance, so brightness alone does not indicate distance.
When you look at the night sky, some stars look brighter than others, but that brightness alone does not tell you which star is closer. A star's apparent brightness, how bright it looks from Earth, depends on two things: how much light the star actually produces, its true brightness, and how far away it is. A very powerful star that is extremely far away can look dimmer than a smaller, closer star.
This is the same idea as flashlights: a powerful flashlight far away can look dimmer than a weak flashlight held close to your eyes. Scientists have to carefully measure or calculate a star's real distance using other methods before they can compare true brightness fairly.
Mastery looks like: They can explain that apparent brightness depends on both true brightness and distance, and that brightness alone cannot reveal a star's true distance.
Common stumbles: Assuming the brightest-looking star is always the closest; assuming the dimmest-looking star is always the least powerful.