Hello. You did not enter the text to which this question refers, which makes it impossible for it to be answered. However, I will try to help you in the best possible way.
A textual evidence is information presented in the text that justifies an argument, showing the reason why that argument is being made and proving that it is correct. In this case, to answer your question, it will be necessary to read the entire text and identify the sentence where the author shows why he believes that students at the Bob Bondurant School of High Performance Driving drive better. This evidence can be examples of how these students have a high number of passing tests, a low rate of failing students, a low rate of fined students, among others.