Do you have any reason to believe that the science teacher would be against differentiation? I know that when my DD was in elementary, it was her science teacher who saw her "giftedness" and gave her different types of questions to answer when doing work, or expected more out of her answers than she did from other students in class, and she was in a gifted magnet program. Even with this, we are in the lucky position of both DH and I are science teachers by trade, so we can easily fulfill her never ending list of questions about things.
Since I know most people aren't in our position, I would suggest trying to find a local college student or high school student to act as a mentor if the teacher is unwilling or unable to differentiate.
However, to start with, you could always ask for extension questions from the current topic/lab activity for him to do at home, or to complete in class if he finishes the work given.Often times the extension questions are given in the teacher's editions of the books so it wouldn't be too difficult for the teacher to put something together for him. Since your school has a specific person teaching science rather than the regular classroom teacher, I would hope that this person is actually a science teacher and as such would have a bunch of these sorts of things hanging around their closets waiting to be used. (I know I have tons of them)
Good luck!
