If you don't think you would get good grades at the college then there is literally no point but make sure you're thinking this through and what would be best for you. As someone has already said, it's your choice.
My family also wanted me to go to a different sixth form but I compromised by looking for other options and weighed out the pros and cons of that sixth form with others but I still wanted to go my school, due to the teaching. I hated most of the people of the sixth form but I knew I wanted to be taught by those teachers. I suggest looking at all the options and if that sixth form is the best option for you, totally for it and state why that is to your parents. Tbh I registered on myself but my parents didnt really go against me once they knew they couldnt stop me. It's good to consider your parent opinions but in the end, you know what you want, not your parents.
I have a strict family. Me having my own opinion which they don’t agree with it’s a long process for them to understand and take me seriously and I end up feeling sad. (I hope that makes sense)
Me too tbh but it's really hard to persuade them so the best you can do is show them what you are doing is what you want and is a good choice. I understand how you feel but they wont agree with you for many more things in the future such as uni so it's good to let them know you know what's good for you and give them an opportunity to be understanding. For example, you might face this problem in the future when picking unis, if you want to go tho (e.g. they might want you to stay at home, limiting many of your options) but if you get through this, you know how to face this problem for such important decisions. They need to learn to take you seriously and this will give them a chance to very early on.
Yeah it is hard and I understand what you mean. I keep ignoring the whole sixth form topic when it comes to them asking but I’ll try my hardest next time. I wish I had a more laid back family oh well.
I'm glad you are going to try your hardest - good luck I do too but I still love my family and I know they will respect my decisions eventually and hopefully for uni as well, even if it takes time for them too.