I was told the same thing... what I'm assuming is that they're similar in the sense that they both explore the human behaviour. Philosophy studies more.. musings of the human mind, such as Who am I? What's my purpose? etc. The concepts which it touches are also more delicate and often, there is no answer to the question. You can also start debates within the classroom haha.
Society and culture (based on what I know from Commerce and school propaganda) is a social science, and social sciences study the human behavioral patterns such as why do we do this, and why is there an economy? These questions do have answers (e.g Economies exist in an attempt to achieve a balance between desire (wants) and resources (which are limited.))
Overall though, I'm not too sure ): I'm also in Yr 10 and also stuck at subject selections...
Good luck!