I volunteered to lead an orienteering course for my son's middle school. They purchased a couple of dozen compasses. Most had the needle pointing south.
Instead of red in the shed, it was black in the shack for many. It there a way to fix this? The compasses were nice otherwise and expensive.

Too bad, unfortunately I don't think there is much you can do. You could try to re-magnetize the needle yourself but it would take effort to do right. Disassemble the compass first, remove the needle, de-magnetize, magnetize again (electromagnetic field ideally for both applications), then put it back together. A lot of hassle and little guarantee it's going to work accurately.

Try to follow this video with one: https://www.youtube.com/watch?v=GuIkvUTxYdU But be extremely careful with HDD magnets. Thy could produce dangerous "shrapnel" on contact with another one (there are two inside). Also, if you expose the dark metal under the shiny shell - paint it with nail polish as its dust is carcinogenic. And keep other compasses far enough away to avoid their accidental exposure to the mag.field.

Return to seller or manufacturer? I'll bet REI and other reputable sellers would replace for free.

I wish. It was donation and the purchaser and seller are lost in the ether.

Just a thought. Contact the stateside office of the company that made the compasses, explain the situation and how they will be used, and see if they will fix/swap them. Might even try REI as well, if they carry that brand. The worst is they can say "no."

Everyone likes good PR...

Hikemor's recommendations are on the mark.