Websites like TV tropes (and to a lesser extent Wikipedia) detail the concept of "" In short, it deals with how hopeful, post-modern, or gritty the setting is. (ie are you boyscout 1930s superman, bloodthirsty wolverine, or self-aware Deadpool)
Which era do you want to set the game in? How dark or serious do you want to make this game?
On the dark side, the game could incur serious injury with out the death-spiral taking immediate effect. Think for a moment - a teenager fails at what they're doing, has their ego bruised at school, and are already an outcast due to mutant abilities... Death by teen suicide seems more likely than by super-villain. Major consequences could be less about penalties taking place in that action scene, and more about degrading the character's will and psyche over time. Non-combat scenes become all the more important in keeping spirits up or otherwise helping students. High-school Call of Cthlulu or World of Darkness for a quick analogy.
The exact opposite effect is possible as well. You wouldn't be sending students against real A-list villains - would you? It could be far more, the opponent got away, so you need to do the dishes for a month. A high school where everyone has weird abilities could be mined for a lot of comedy. (Exemplified by the old RPG "Teenagers from Outer Space") By existing in a comic book universe where no one stays dead at the whims of the great artist in the sky and real guns don't exist because they're "imitate-able acts" so characters don't stay hurt.
A middle road might be allowing the spiral as a way to emphasize that the players need to be a team (or earn social points in the other half of the game) to offset the great danger of combat. Additional mechanics like spendable hero-points or luck rolls might be an option as well.