The Inaugural Teaching Topic

So I'm teaching class 7 science and some math, which is great I know most of the kids and behaviour wise they have been good to me so far.  The first science topic was drugs, HIV/AIDS and then they wanted to cover rape.  Many of the names of drugs are different here, miraa, bhang, etc.  I neglected to tell them they sell drugs in front of my house at home. So it was a nice light topic to start with. I think they know more about HIV/AIDS than I do. Now if I can just remember the rules for adding, subtracting, multiplying and dividing fractions I'd be good.