Not to defend racists or imply this is acceptable in any way but everybody does stupid shit when they're a teenager and something like this shouldn't haunt them for the rest of their working lives provided they mature into well-adjusted adults.
The bigger problem is the poorly-adjusted adults in the communities that raise these kids and teach them to be hateful towards people with harmless differences.
The letters they are holding were provided by the school for some kind of event. It seems like these kids thought they could be funny by spelling out a no no word. To any rational thinking human, this isn't funny, but teenagers aren't rational think humans. That's pretty much the definition of puberty.
But it's 2024 and kids post everything online, so now it's gone viral and everyone judges them as racist scum that deserve to never get a job in their lives. Off of a single photo.