dropping a gcse in year 11?

Back in year 9, i made the decision to take GCSE design technology/product design. at first i enjoyed it, but i had almost entirely cover lessons in my first few terms so did not have a good judgement on what the subject would be like with the actual teacher. by the time i was aware, we had passed the deadline to change the options. anyway, i feel as though i have not learnt any of the content, and i have no idea what i am doing within the lessons. we haven’t done theory work at all since probably term 2 of year 10, and have been instructed to do it as homework from a textbook that is incredibly difficult to comprehend.

recently we had our mocks, and i got a grade 5. this is more or less what i expected, i felt as though i did horribly in the test. the teacher (who for some reason predicted me an 8 despite never achieving anywhere near that) privately spoke to me and threatened to report my poor grade to my head of year, and essentially told me i would fail my exams in the summer.

due to all of this, i am thinking of dropping the subject, however i do not know how well the conversation would go with my parents or teachers, especially as i am regarded as a very good student in all my other subjects. but i do not feel like i can continue the subject, it has had horrible impacts on my mental well-being and i simply cannot cope with it anymore.

what should i do? and how might i be able to have this conversation with my parents and school?