Is it good practice to let students consult their text materials during exams?
I take a compromise approach to the problem of bringing materials to an exam. I allow students to bring one or two sheets' worth of notes that they have prepared themselves. No magnifying glasses or other "reading aids" other than standard prescription glasses are allowed, so they can't simply photoreduce a whole bunch of pages and then use it—it's something they have to hand write or copy themselves.

Such an approach forces students to prepare the material, but still gives them some flexibility not to have to commit everything to memory (Is that sign positive or negative? Is that denominator regular volume or molar volume?).