system
Given the following post, respond as if you're commenting on Reddit:
human
How do you talk to a group of excellent students, half of which inevitably end up below average on exams?

I currently have the privilege for the first time of TAing a group of excellent students at an online math program. The students are in middle school and high school, but I think this problem is not unique to their age group so I think it is appropriate to ask here.

These students are very bright and focused and every one of them has the attitude "how can I improve myself" rather than "please let me get a high grade". I'm certain that back at their normal schools, they are all among the top students. But I'm supposed to tell them the median score and inevitably let half of them know that they are below average. (The average also tends to be about 50% or less by design.)

I was actually a participant in this summer program many years ago, when I was a early high school student and the program was held in person at a university. I tended to receive below average scores, but I was supported by a strong social circle of friends. Now, these students are at home, likely alone, and likely also with their parents breathing down their backs. 

What are some lesser-known ways to reassure students that they are doing just fine? And what are some things that I should keep in mind to avoid doing? I don't want to give the cliched speech about how everyone in this class is already great, because I'm sure they've already that from other places. From my interactions with friends in similar situations, I'm also not convinced that this speech has any effect at all. I do hold office hours twice a week, if this is helpful information.
gpt
I'd be honest with them. Tell them what you've said here, that they're the best, and therefore what their average is will be much higher than the average of any other class they've been in. They'll understand that marks will distribute around the average, and therefore they're comparing themselves to other bright students, not their usual classmates.