What happens? Its obvious parents sacrifice so much to see their children comfortable and happy.For instance parents starve to be able to provide for their kids .A literally proven example is the rate of consumption of foodstuffs during school days and the opposite during holidays.A bread vendor easily lacks supplies during  holidays while the opposite is true he also lacks market on school days.It clearly explains that parents strive to provide comfort to their kids but they can't enjoy that comfort alone.This is clear reason enough to explain to kids that they need to do their best in school to make their parents happy