This is correct grammar. To rephrase for clarity:
...and together they help create a text that genuinely meets the needs of a student.
I would agree with you that the choice to meet a single student's needs is an odd one. But one cannot quibble with the authors' intended meaning. Perhaps they wrote this book only for Rosa in seat 14!
I'm joking, of course. The authors probably chose to use the singular "student needs" to align with the earlier singular usage in "student-focused". In their view, it would be awkward to switch from singular to plural or plural possessive. However, I agree with you. If they are trying to appeal to the needs of all the students, they should have said it plainly,
...and together they help create a text that genuinely meets the students' needs.
That said, there is nothing grammatically incorrect in their choice.