Partly home issues, partly school ones. The one constant is lack of investment.
The vast majority of parents really love their kids. However, some of them simply don’t have the time or energy to insist (for eg) that kids do homework. Some see zero point in school work so don’t encourage working hard in school. Many parents work in low paying jobs so struggle to ensure kids come to school having eaten nutritious food and many kids lack extras (such as having a car to get to a football training session) and therefore don’t exercise.
Then there’s schools. In these areas they don’t have the money to attract decent teachers. Who the heck is going to choose to teach a class of 30 where there’s 2 with social workers cos their home life is really not okay, 4 with emotional / MH issues, 3 with significant behaviour issues and probably another 3 with undiagnosed SEN? With no additional pay for being in a tough school, but more abuse (cos the kids are dysregulated) and being hammered by ofsted?
When there’s a child who cannot cope in mainstream school and they need alternative provision the school get financially penalised. The grammar school I taught in paid for AP not even once in 5 years. Current (northern, disadvantaged, mostly white working class) has more than one kid in every year group in AP. And it’s not cos I magically became a shit teacher when I started work here. Keeping children who cannot cope with a classroom in a mainstream setting has a hugely negative effect on that child, their family and their classmates. It is wrong and unfair that there is insufficient access to suitable school for kids who can’t cope.
Why is this affecting girls more than boys? I think it is puberty. By the end of year 10 lots have girls are more mature and are taking school seriously. But (on average) for boys the change happens later. Biology is a bitch sometimes. Then there’s the usual social issues of boys being less compliant (cos “boys will be boys, innit”) and a significant lack of fathers (which I expect affects boys more than girls cos role models are very important).
Sorry, that was long! TLDR: some people are proper skint and the public sector needs more money.