Here are my thoughts, because I remember very clearly being the teenager who was bright (in the subjects I liked) but lazy, whose mum was a teacher. Throughout childhood I longed for independence: the only thing I wanted was to be grown up and free.
From as young as four years old I remember resisting fiercely whenever I felt I was being "made" to do something. If for example my mum said in a bright encouraging tone "today we're going to start writing a diary", I sensed from the exaggerated tone that I was going to be made to do this whether I wanted it or not; that it was a restriction on my freedom; and I remember the realisation every single day out would always be followed by having to write about it.
Whenever my mum tried to give me advice, instead of hearing what she had to say, I only heard the nagging tone, felt the restrictions on my freedom, the ruining of holidays by being made to study, etc. I actually dreaded holidays as a teenager because they symbolised being at home to be nagged, especially the half term in May (just before exams). I would often listen to other people, but I always had difficulty taking advice from my mum, perhaps because it was always very emotional on both sides.
My mum was a secondary school teacher and so wouldn't stop pressing me about school work; the more she nagged and interfered, asked me about homework, asked the dreaded "how did your mark compare with the others in the class", the more I rebelled. I loved foreign languages and science subjects, but I loathed essay subjects such as English, history and religious studies, dismissing them as pointless, and did as little work for them as I could. I especially despised any that needed research or reading. It became easier in year 10 when I was able to drop some of them; only then did I gain enough self-discipline to work hard. I got reasonable GCSEs and A-levels, which were good enough for university, but only now in my 30s do I start wondering if I would have got all A's if I'd worked harder.
To be fair to my mum, though, I keep wondering what she might have done differently to motivate me; I found out later that one of her tactics was to secretly get other family members such as grandparents to encourage me. For all I know, her asking them to help might have been very tearful indeed, but if so, she did spare me this. Getting other people on board did work because they would be less emotionally attached, and I was more likely to listen to them. I did feel a bit cheated when I found out, but it hindsight it was probably one of the best things she did. My dad (not a teacher) did once hint that it was very hard for her, as she was a teacher.
I also think I might have done differently if I had learned more about careers (though perhaps not hearing it from my mum), in particular which ones are well-paid. Although there was a lot of careers support at my school, nothing much was said about pay; it was all about entry requirements and qualifications. If I had used the possibility of a well-paid job to motivate myself, rather than simply stopping mum nagging me, things might have been different.