Parents are mainly responsible but we have to keep in mind they have a limited window before the kids are fed into the educational system and the wider culture. If your child is not at least somewhat disciplined before they go to school full time, the system is not going to correct that. By this I mean, can sit still for a short period of time and focus, take orders from elders, not be glued to their smart phone, or at least be in some 'fear' of repercussions for their bad behaviour. Once they are in the educational system, you're not seeing them for most of the day and their teachers, course material, and friends become very prominent in their lives.
The shortcomings of the educational system would be another thread. Most of my family members are in the educational field, from teaching in Harlem, NYC to wealthier schools in the the suburbs. I just finished getting my kids through the educational python. If you don't know there is a problem in the schools, discipline being one of the major ones, you are not looking or do not know. If you don't think the 'evolution of culture' in the last 30 - 40 years does not have a effect well you might not be realistic.
A progressive push to soften school discipline has caused student suspensions to plummet — and made classrooms more chaotic and dangerous than ever, parents and teachers charge.
nypost.com