Rigor redifined

i have read an article called "Rigor Redefined" by Tony Wagner. What is the topic being discussed? The topic is the schooling students need. What is the main idea? main idea is that are we teaching them the right stuff? But are we teaching them to ask good questions/or think for themselves. I thought was is rigor? I researched on dictionary.com and rigor is strictness or dealing with things to the maximum.