You should be writing the Objective in a consistent tense. Your first sentence is written in 3rd person, and the rest in 1st person. Just stick to 1st person. I don't think secondary school matters at all, and I daresay the same for Senior Secondary. Instead of just listing courses, I recommend explaining a bit what you DID in those courses--projects, lessons learned, challenges, etc. Finally, include a skills section (which should be consistent with what you explain about your course work). If you have any personal projects or volunteer work, put that too. If not, focus on the stuff you did at school and the skills you applied (e.g. you claim to have 2 years of Python experience, but what do you have to prove it? Course work? Projects?).