OP, I haven't read the thread yet because I don't want my response to your post to be influenced by other people's comments.
I can identify with your post in many ways but you have made me very angry!
First, I, too, took an entrance exam for independent school. I was ten, just, because my mother (who left school at fourteen) thought that as a 'genius' I should pass entrance a year early. My very ordinary church primary prepped me by going through all the maths work, but no-one thought I'd have any problem with the English. When I got there, the topic for creative writing was 'Paris in the Spring.' For a northern, working class girl in the 1960s. Had never been to France, very little knowledge of Paris, no idea how to approach that kind of writing... I gave it a go but I failed. I didn't get a place and my mother never again claimed I was a 'genius' (Mensa tested IQ 156 - its respectable, even so). Saw much duller girls go off to the independent a year later, while I went to the local sink-school, five minutes from home, surrounded by hills and trees but nothing on offer in the way of education. I used to turn off my brain as I went through the school gates in the morning. I didn't waste my life blaming other people, though.
So, some years later, finding myself unexpectedly the single mother of a four year old, with an income of £200 a month (not much, even in 1986) I organised myself to go to university with the few qualifications I had (because the grant would double my income), got my degree and eventually did teacher training and got a (fairly well-paid) job. It wasn't easy. When I put it into a novel you can read all about it, its too long for here. But I wasn't sitting on my arse being sorry for myself. And I did all this whilst having undiagnosed mental health issues, being depressed and suicidal and although I didn't know it at the time, coping with my lifelong disability (HFA/Aspergers) which is prevalent in my family.
Teaching, in two of the most deprived areas in the UK, for 21 years, I met a lot of young people from those deprived areas, whose families had no education and did not value their children's schooling. Most of them were like you, happy to moan about the school and blame everyone else that they weren't rich and comfortably-placed in life. Some, however, were hard-working, determined, wonderful individuals who knew that school, even in our deprived area, was a great opportunity and therefore took advantage of it. I recall one girl from a tutor group of mine - she left school with a CV that looked like she'd been to a top independent school. She'd been on every trip, applied for and achieved internships, passed her exams, proved her extra-curricular commitment - and she was only one of many. She wasn't moaning about who she was and where she came from - she was getting on with being the best she could be.
My child's education? She went into independent at 11. I worked my balls off at a job I hated, that hurt me every day, to make sure I could pay what I had to. She worked her little socks of being the best student she could and taking advantage of extra-curricular activities etc. She's still friends with some of her teachers and she's 33 now. All those years of effort and having the right attitude did not come to nothing - she has the nice, middle-class life that she wanted.
Now to you. You write well. So well that I find myself wondering if in fact you have had a university education that you haven't bothered to mention here. Taking your OP at face-value, believing every word, here is my advice.
Get off your backside.
Get yourself into university - you can be ready for next September if you start now.
Get on with your fucking life.
Excuse me. I've been immobile with depression for years. Suddenly, I feel as if I can do something about it. I'm off now to get on with my fucking life, too.