The letter is directed to the teacher who taught the daughter's programming class during her last year in the US, and all the incidents that the mother mentions

The letter is directed to the teacher who taught the daughter's programming class during her last year in the US, and all the incidents that the mother mentions occurred in this US class: "During the first semester of my daughter's junior/senior year, she took her first programming class." -- We are told she finished early; therefore, we can assume that the "junior/senior" usage denotes the last year she was in the US. The daughter is currently attending high school in India not because she necessarily needs to but rather because it is a learning experience before college: "My daughter ... is now attending high school in India as her 'gap year' before heading off to college."