Some "high paying" career options after 12th (science stream) for a boy coming from a very middle class family who has got good marks in 10th and 12th (science stream)??
The best option that you have if you are seeking for a high paying job as a career and if you have done 12th with science then you can go for engineering degree. If you can get into admission in any top IITs or NITs then you can get a very handsome package in any MNC after completing engineering. But for that you will have to crack JEE mains and advance examination with very good rank then only you will be able to secure admission in top engineering colleges of India like IIT Bombay, IIT Delhi , IIT kharagpur etc. After completing your 4 year B.Tech degree you will get placement option where you can get placement in any good engineering college.
I hope this helps.
As you get good marks you can definitely clear exams like JEE mains/Advanced and NEET for engineering and medical courses as usually the top government colleges take less fees and give merit scholarships. Other than this if you are interested in other fields you can give UPSC, railway and bank exams also to get a secure good paying job.