Some people say that children are diplomats, which makes sense. People are born with the ability to socialize.
The reason why you didn't integrate into the group is because you didn't find your own strengths and lacked self-confidence.
I suggest you chat with a classmate first, communicate more, treat it sincerely, and gradually expand your social scope.
You can try to keep a diary, praise yourself every day and gradually improve your confidence.
In the student stage, the most important thing is to study, actively consult with classmates, listen carefully in class and actively answer teachers' questions. I believe your grades will get better and better. Teachers and classmates will find your progress and help you integrate into the group.
No one will look down on a hard-working student, even if his grades are not ideal, he can be respected.
I wish you success in your studies!