No, in many cases I don’t understand why teens are being deemed as helpless victims unable to make decisions for themselves
There is a spectrum between 'helpless victim unable to make decisions for themselves' and that idea that a teenager - or all teenagers - will have the same capacity or access as an adult to make choices. Both by biology and social structures, teenagers in school don't.
I entirely agreed with you on OP how deprivation can in many ways not be connected to the parents' income - it very much can, but also children with well to do parents don't automatically have access to everything their parents have, but that also includes the support to get education or anything else. Something I was discussing in a meeting today with school staff was the inclusion of vulnerable students that aren't eligible to pupil premium and the work done to identify them.
When I was a teenager, I literally spent weeks without an adult in the home. I also had an undertreated trauma disorder and physical disability (many disabled children still face barriers to accessing education). There were days I was very late for school because between that disorder, the executive dysfunction, the pain, and just not having anyone in my home who gave a fuck if I did, getting out of bed was fucking hard. You could frame it as a choice, that I was "old enough" as I too often heard, but it wasn't a free choice. I didn't have the resources or the well-being to make better choices and I had no support. As an adult, I still have multiple supports that I've put in place to help me get up even on days where everything hurts, but teen me didn't have access to that.
I also finished school in one of the most well-to-do school in the metro area, the only A rated school, the one people spent over 5k in property tax a year so their kids could go there, but I was largely left to struggle because it was a nice area and I was - as a police officer once told me when I told him at 15 that I hadn't seen a parent in 3 weeks - "old enough". All that led me to feel is that no one cared when shite happened I was 6, definitely no one is going to care when the same shite happened when I was 16 and I gave up asking for help from adults. I got plenty from other teenagers, many who had supportive parents, but adults directly, no. I lived down to their expectations of me.
Those who work in schools or in similar spaces have to be aware and vigilent to these issues in children - including teenagers - to be able to deal with deprivation. Income does play a significant but it isn't the only role -- but age isn't a reason to write off kids as just making bad choices. We should do better than that.