Final answer:
The passage's evidence that supports funding the arts includes studies showing music programs improve academic grades and data indicating increased college attendance and graduation rates among music students.
Step-by-step explanation:
The two details that best provide evidence in support of the author's thesis in the passage about funding the arts are: First, the numerous studies showing that prolonged enrollment in music programs improves grades for students, and second, the available data showing that students who play a musical instrument for an extended period of time are twice as likely to attend and graduate from college as non-musical students. These pieces of evidence underline the significance of music programs in enhancing academic performance and college graduation rates, thereby countering the argument of music being an expendable accessory in education.