I left school at 16 with 3 standard grades (Scottish GCSE equivalents) not because I'm stupid, but because I was desperate to be out of school, I didn't work, I didn't attend and I didn't bother turning up for half my exams.
I couldn't get a job, so went on a YT course which turned into working full time hours for the princely sum of £40 a week. 
I then found myself pregnant with my DS, stayed at home with him while my DP worked, had my DD (she was planned, lol) and discovered that although I'm literate and numerate, with no qualifications I was struggling to even get a job as a cleaner or a checkout operator...Why take on someone who couldn't be bothered at school when there are younger, cheaper (minimum wage changes as you get older) employees who did get qualifications.
I've ended up spending the last five years in college and uni, just to catch up with people who left school at the same age as me, but with better exam marks. It's so much harder now than it would have been to just work then, especially with kids.
I'm lucky that my DP has been able to support us while I did all that, but if at any point I'd ended up on benefits, with or without having children - there's no way I'd have been able to do my degree, it just costs too much and I'd still be struggling to find a crappy minimum wage job.
Without qualifications, especially in this day and age - you're unemployable.