Teacher unions (as did other unions) supported O'Malley in his gubernatorial campaigns. You can find out more about the MSEA here.
What I posted was not a position paper, but recognition from the NEA. I assume you know who that national union represents. O'Malley is only the third governor to be so recognized.
O'Malley fully supports unions and collective bargaining. He has made that case publicly many times. He is also opposed to vouchers for private schools. He believes that the public school system is the basis of democracy in America.
When he was mayor of Baltimore, he sent his children to private schools. I do not believe that fact is germane to his positions regarding public education. You could write volumes about issues in Baltimore public schools. My kids attended public schools in Maryland and received an excellent education. Maryland has some of the best public schools in the country, and this can be attributed in part to Martin O'Malley's vigilance in supporting them through funding.
As to NCLB, that was a federal mandate linked to federal funds for state schools. As of 2012, Maryland was one of 32 states that was granted a waiver from NCLB. Unfortunately, these waivers are highly complex and require a whole lot of paperwork and renewals. I believe that NCLB and its descendents should be addressed on the federal level, where they came from in the first place. Perhaps Senator Sanders is in a position to propose legislation in that regard.
As it is, states are finding all sorts of difficulties with complying with these waivers. The fault for that lies with Arne Duncan and the Obama administration.