Ask him to learn as many words and grammar sentences as possible every day, preferably about the words he learned today. Because he doesn't even know basic words, he should master primary school English vocabulary and gradually deepen the difficulty. Don't ask him to master too much at once. Communicate with parents and strengthen supervision. Sometimes you have to force yourself to learn English. Let him read a short article every day, just one. If you don't know the words, let him look them up and then let him translate them. Get to the point. He is required to listen to English for an hour every day. There is no need to set a time. Being as free as listening to music is a good thing. Let him watch, read and understand the articles in the textbook every day from grade one. If you understand the main idea, try to remove some keywords so that he can remember to fill in. Slowly, you should be able to improve your score.