This is what I think of when I think of "early life stress" in kids - not worrying about school.

It's called "Adverse Childhood Experiences", or ACEs, and the field of psychology has found them to be extremely good predictors of future negative outcomes for a long time now.

https://pmc.ncbi.nlm.nih.gov/articles/PMC8882933/

Things like abuse, neglect, natural disasters, basically anything that can cause trauma or significant stress.

Be a toddler and your mom's new boyfriend abuses both of you? Congrats, you brain has developed in a way that will not be conducive at all to your future, because instead of developing a functional reward system, you've developed a specific hyperawareness to manage the difficulty of living around one kind of abuser. This incredibly specific adaptation will of course, not prevent you from being an easy target for an entirely different type of abuser in high school.

(It's actually not that simple of course. Multiple ACEs are predictive of future troubles, not just one, so it's more like "A child who lives in an environment of constant stress, fear, and pain is likely to have a brain that didn't develop well" with a direction of effect unstated)

This is one reason why things like abuse and poverty are so damn cyclical. Your parents grew up in poverty and with abusive parents, so they have an elevated chance to abuse their children, and on and on and on.

This is also one reason why something like "Free food at school for anyone who wants it" is so damn effective, because it eliminates an entire class of ACEs from all those kids, and in the US, it also eliminates the horrific humiliation machine we've built around paying for school lunch, which might not be the best way to raise kids anyway.