You can choose any of science ,commerce or arts stream based on your interest after your 10th for your 11th and 12th and then for graduation if you want to become an IAS officer.
This is because,
to become an IAS officer you need to clear UPSC civil services examination and to be eligible for UPSC examination there is no compulsion to have done 10+2 in a particular stream , also there's no compulsion to be a graduate in a particular subject, all you need to be eligible is that:-
you should be a graduate in any discipline and 21- 32 years old , so you are free to do 10+2 and graduation in any subject.You can check upsc eligibility criteria at https://competition.careers360.com/articles/upsc-ias-eligibility-criteria/amp
choosing Arts or the humanities in your 11 and 12th and graduation can be really helpful for your UPSC examination, this is because in Arts you will be learning subjects like history , polity etc which are a part of the UPSC syllabus so it will help you in your upsc examination.
To help you further here's a brief of your UPSC exam pattern
UPSC civil services examination has 3 stages listed below :-
******prelims exam :- it is objective paper and is of qualifying nature , so you just need to at least qualify it to be eligible for mains examination, the score /marks obtained by you in your prelims examination is not added up or used in your final merit. Your prelims exam consist of 2 papers: -
-) general studies 1
-) general studies II ( csat )
You get 2 hours for each paper
******Mains exam. :- it is descriptive /written examination . There are a total of 9 papers which are listed below:-
-) compulsory indian language.
-) general studies I
-) general studies II
-) general studies III
-) general studies IV
-) optional I
-) optional II
The compulsory indian language and english are qualifying in nature . You just need to qualify them. The marks obtained by you in these two papers will not be counted towards merit list.
******Interview :- After qualifying mains, you have to go through interview round, and it is more of test of your personality rather than knowledge.
For detailed information , go through