Richard Branston started Virgin working out of a basement on no money and little food. The only reason Virgin is what it is today is because of ridiculously hard work.
Einstein may not have liked school but he worked day and night on his theory of relativity.
Thomas Edison made multiple attempts at creating the light bulb, it didn't suddenly turn up one day out of nowhere.
Hard work does not equate harder homework, or slave work as some may argue. Hard work means putting all you've got into pursuing your dream or calling, and more. It's dedication, ardent fervor, passion and never accepting no for an answer. It is the only key to success worth wielding.
If you're talking about giving "school age" children harder work or wanting them to work harder, then no, hard work is not the key to success. Research proves that people of all ages learn best when they are self-motivated. Brilliant people have not liked school. Thomas Edison, for example, dropped out of school. Albert Einstein hated school and learned DESPITE of it and not because it. All of this can be read in Reader's Digest January 2014 issue.
What kind of drugs are you on or are you living immediately post WWII? The standard of work hard and have a decent life actually has always been a degradation for immigrants that if they didn't make it in America, they just didn't work hard enough, but we all know immigrants and slaves broke their backs making this nation and making it so damn rich.