That depends on what grade you're in now. Senior year is twelfth grade. (Junior is eleventh, sophomore is tenth, and freshman is ninth.) Most people are 17 or 18 when they graduate, depending on when their birthday is.
Staff engineer is one grade for the position of engineer. Most companies have a grade system for engineers, ranking from low to high as follows: Engineer Senior Engineer Staff Engineer Senior Staff Engineer Principal Engineer
Depending in which grade level a high school student is in, the subject of tensors in Senior Mathematics may vary. Mostly, the tensor analysis is covered between Grade 9-12. More intensely in grade 12, when Mathematics is taken as a specialized subject.