CBSE 12th

The Indian Institute of Astrophysics is a premier institute devoted to research in astronomy, astrophysics and related physics. Institute runs a full-time research programme where in the students work towards their Ph.D. degree under the supervision of an IIA faculty. Students may join the programme in either the first semester beginning in August or the second semester beginning in January. Entrance examination is held in December followed by interview in January. Students passing the JEST exam are interviewed in May / June. The eligibility criteria for PhD at IIA is M.Sc in mathematics / applied physics / applied mathematics / optics and photonics / instrumentation / electronics, etc. All around excellent academic performance from 12th to PG will help you fulfill your dream.
Indian Institute of Astrophysics also conducts the Integrated M.Tech- Ph.D (Tech.) programme in Astronomical Instrumentation in collaboration with Department of Applied Optics and Photonics, University of Calcutta (CU). The Degree will be awarded by the University of Calcutta. The duration of M.Tech course work will be of 2 years divided into 4 semesters. After successful completion of the M. Tech course a student can opt for registration for Ph.D (Tech.) programme, subjected to a selection procedure and minimum cut-off grade.
The Integrated M.Tech - Ph.D (Tech.) Programme will admit bright, highly motivated students with a three years B.Tech. degree (Post B.Sc Hons) in Optics and Optoelectronics / Radio Physics and Electronics from CU or B.Tech / BE degree in Electrical/ Instrumentation/ Electronics and Communications /Computer Science and Engineering from an institution recognized by AICTE. A candidate with M.Sc degree in physics / electronic science / applied mathematics /applied physics from a UGC recognized institution is also eligible to apply.
You are advised to take PCM subjects in 10+2 board. After that you can take either engineering or science route to fulfill your dream.

Commerce and science are the two broad categories. In commerce, you can opt for arts/design, business, finance and banking courses.
In science, you have engineering and medical. These are the traditional streams which students choose. Some new streams are also in demand nowadays like biotechnology, nanotechnology, agriculture and genetics. Students are also moving towards fashion designing and interior designing. Research-oriented students can go for KVPY and get admission in institutes like IISC, IISERs, etc. Commerce students can go for CA.
There are courses like mechanical/ electrical and computer science in engineering to newer ones like hotel management and fashion designing. You can opt for any of these as per your interest.
Kindly upvote this answer.