As for English grammar, it's really not that important. Just make sure you have a sense of language. If you are conscious enough, you can buy a grammar book and read it slowly, so that you can test the grammar of multiple-choice questions, and that's all.
If the teacher is not bad, just study science with the teacher. If you are not at ease, it is still recommended to do "experimental research";
As for classroom efficiency, it is not difficult to concentrate if you really want to learn. It is suggested that you can ask questions silently in front of the teacher.
In short, calm down, slow and steady, and wish you success in the college entrance examination.