What year did i start high school if i graduate in 2019?

2012

Step-by-step explanation:

If you start high school education in the year 2012 then, you can complete your education up to graduation in the following session.

(1). 2012-2013 → Ninth (Starting of high school education)

(2). 2013-2014 → Tenth

(3). 2014-2015 → Eleventh

(4). 2015-2016 → Twelfth

(5). 2016-2019 → Graduation

Hence you can start high school in the year 2012.

You would have started high school in 2015