Explain how hard you are finding settling in and try and come to a compromise with them: if you agree to work harder your parents may give you some freedom at the weekend. Ultimately the trick is to make them feel confident that they themselves are making the right decision - that is what writing to persuade is all about.
You may also like Encourages talk with adults, tries to see both sides of the situation and reassures the teenager that his parents care.
This includes both your use of vocabulary and of specific literary techniques such as direct address and rhetorical questions to draw the reader in and persuade them to feel personally involved and implicated by your suggestions.
I appreciate that this is not an easy thing to do but you could talk to your form tutor, maybe you could be moved to a different table where you can make new friends, or you could join a club or team.
Use plenty of adjectives and adverbs to push the reader towards your point of view - if you are writing to persuade them to donate to a charity for example, an adjective-rich sentence like this will be much more effective than the same sentence without the words in bold: "It is almost completely impossible to describe the immense impact of generous charitable donations on the poverty-stricken lives of the brave people who live in these savagely war-torn areas.
For instance, the park might well be a wonderful natural habitat; but it also likely costs a lot to maintain; and it might be a good place to walk; but the town is clogged with cars.