YA novel / short story (?): Boy trips rival who gets seriously injured

Dears,

Here's a memory snippet that keeps nagging me, however, I'm unable to pinpoint if it was a short story or an episode within a novel. Anyhow, here's the story: a boy plans to take out his rival (the school bully?) during a cross country run. Her puts up a concealed (barbed?) wire across the trail (maybe an illegal shortcut he knows that boy would take). The ploy works beyond his expectations though: the other boy cuts his leg on the wire and gets blood poisoning or tetanus, losing his leg or even dying, leaving the other one guilt-ridden for life.

Does this ring a bell with anyone?

A similar episode plays out in John Knowles, A Separate Peace, minus the cross-country run and the planning (from what I recall)

Hi glaciergoat,
I am awfully sorry, I've only just noticed that I never thanked you for your suggestion. I cecked and ruled out "A separate peace" at the time, and then sadly forgot to post my feedback. So: thank you very much, and please accept my apologies!
... and I'm still searching.