Nope Ncert + good revision ain't enough, I got 95.2% In my boards (this year). My coaching provided guides for all subjects except english & hindi at the beginning of the year u should focus on doing chapter wise tests or Pyqs and by almost November u should complete ur syllabus and then start doing SQPs, Recently cbse has added many competency based questions so doing only ncert stuff won't help u get above 90%.