I've been strongly recommending tadoku to people interested in learning English whichever generations they belong to, regardless of their age or level, and I found it the most challenging when I do it with high schoolers, who have close to grown-up mind and curiosity but with low level of English competence. The gap between what they want to read and what they can read seems insurmountable.
Then, if youngsters are capable of reading an English book for a certain period of time, I rather recommend English version of Japanese Light novels, ラノベ, than books for native English speaking children and adults. The language and expressions used in the light novels are much simpler and plain, I think.
Here is a site that you can make a sweep search what light novels are available with English version. They are marked with *. I've got to warn you that the site is like a quicksand, a mud or a hagenomyia? that you won't be able to drag yourself up easily once you're hooked up with one of the themes, I'm afraid...
(forgot to mention at first^^;)
Now, you have much easier way to see what the light novel English translation is like. I guess you'll find these kind of moe covers at the small corner of Jyuken Eigo section at bookstores. I'm sure these might grasp tight the heart of some otaku high schoolers than boring textbooks at school.
(Actually, many fans are translating Japanese light novels by now and some of the translations are amazingly good, since in many cases the translators themselves are big fans of those novels that they won't give up on hallways and works with them hard to their heart's content. I happened to find a translation of No. * , I bet you can tell what * means if you're a fan of anime now, I'm eagerly following a new release.)