Hello Jayant

As you are in 11th class so there are very less number of competitive exams this time you can give 

Here I am providing you the list

SSc MTS ( nulti tasking staff)

Eligibility 10th and 18 years old

SSC CHSL ( combined higher secondary level )

Eligibility 12th and 18 years old

Raiway Recruitment board RRB D class posts

Eligibility 10th and 12th

After your graduation you have number of competitive exams like as

UPSC CSE  to become IAS, IPS and other civil service officer

SSC CGL ( Combined graduate level)

Bank exams like SBI PO, SBI clerk, IBPS, RBI Grade B etc

RRB graduate level exam

And Other state level exams

this time you should focus on your studies and make your base good so that you can easily crack any exam in future 

Good luck!

Hy Jayant 

As most of the competitive exams require at least 12th grade education , the ones which you can give on metric basis are - 

1.Scheme for Early Attraction of Talent (SEATS):

2.BrainX National Maths Contest

3.NSO, NCO, NSS, UCO, USS and other olympiads in maths and science

4. Scholarship for Higher Education (SHE)

5. Tata Building India School English Essay Competition

Apart from these you can give KVYP ,  NSTSE' IGO etc scholarship exams.

HOPE it HELPS 

ALL the BEST