Please check it out my grammatical mistakes.

I have started writing story of the most of my friends and mine too. Please check it out my grammatical errors.

At the innocent age of 3 years all of us go to school and at the age of 15 years reach XI class. According to their own interest or their parents interest some students are opt Commerce, Some students opt art as well as some are opt Science and complete their schooling at the age of 17. After completing schools most of the science stream student take drop of one year or more than one year for IIT-JEE or NEET preparation. These are competitive exams is conducted by government but success ratio of these competition is very less. A few student is selected and remaining students try to get admission in private Engineering colleges.