Yes, I remember when my son failed maths in the first test. We made him read every day after dinner, without a phone, and on the second he passed with 4 points more. They can't reverse that first result, but you can fix it with regular work.
The same thing happens in our schools. My daughter's cousin retook math last year because he failed the first exam, and by sitting down every afternoon with the book without a cell phone, he went up 5 points in the second. The first result does not go back, but the work fixes a lot.
Yes, Thomas, I know as you say. I also forced mine to read after dinner without a phone, but he couldn't last more than three days. In the end he succeeded by private evidence, not by compulsion. How many points did your son get in the second?