Depends on the teacher. It has to be one that meets the requirements of the SD course - e.g. one that allows you to program GUIs, one that is object oriented etc.
So unfortunately the answer is.... I can't really say. A lot of schools use Visual Basic (VB) and more are starting to use Python as an alternative. Some use the higher level languages such as C# and C++, kudos to the students that actually get it but I find it is quite unreasonable as an entry language for students. Further discussion re suitability of programming languages in SD can be found
here.
Best thing to do would be to ask the current software development teacher at your school as to what language they use, and go from there. SD teachers don't like to deviate away from what they already know - it takes a significant amount of effort to learn a new language. If your SD teacher has been doing it for a while, chances are you'll get them teaching you and the language they prefer/currently use.
Cheers