Mihir Garud left a job as a stockbroker to teach personal finance at a Chicago charter school. He's also the treasurer of a union that now represents 25% of charter school teachers in the city. Garud, who sees unions as the "last brake" on a system of free market capitalism run amok, turns out to have a lot in common with the teachers in Chicago who organized the country's first just-for-teachers union back in 1897.