The why is always challenging. We notice this. Anyone who works with children knows that they are more busy during the school year. When school get's out, there's just less busyness. I think it has a lot to do with the fact that school is like a job for kids. School has your co-workers, your boss, your supervisor, your overtime, which is homework, and your hours. What you don't get often and what kids fail to recognize are the benefits, which are like wages.
School is a big deal. A study in 2014 showed that 84% of children reported that school causes them anxiety. There are so many things that schools could do better. There are things like changing the hours of service, lessening the amount of homework, providing access to mental health curriculum, creating safe spaces for kids who are neuroatypical and those types of things. There are so many things that schools could do.
I think you could just ask a random sampling of 10 kids what they think schools could do better and you would get a host of responses. School is just a really stressful thing for kids. We see a 60% increase in suicides during school days. In the ERs we see 100% to 150% more kids on school days than on non-school days.