It would depend on the maturity of your students, as well as their age. I read this novel in the 10th garde, but it was a gift from a teacher, because I had been looking for a copy for well over a year. Make sure they are at least in highschool, because as you know it is quite graphic in nature, and the last half will most likely bore them as it doesn't have any smut in it.... At 15 or 16, most will have enough maturity to deal with the subject matter. If you wanted to quicken the teaching, the 1997 film with the "rape" of Humbert by Dolores omitted is just as useful in starting class discussions, and will spark interest in those that would like to read it.