For the record, I am mortally tired of people yelling "racism" every time Obama hits a bump in the road. It amounts to an attempt to delegitimize the opposition, which is very undemocratic. The duty of the Opposition is to oppose, as Disraeli said. Opposition may be tactical or principled, but it is not unpatriotic. The people who oppose Obama's initiatives on health care, on union elections, on cap-and-trade, on foreign policy or investigating the CIA, don't care that he's black. They just don't like his proposals, is all.
Some of Obama's more innocuous moves -- like addressing schoolchildren -- raise hackles on the other side because of the belief many have that he wants to move the country toward socialism, and toward that end is interested in expanding government so as to intrude upon people's lives. They see his every move as a gambit to establish greater control over the lives of our citizens.
This belief (whether you subscribe to it or not) intersects with another common belief many also have that there are lots of people who would use the public schools to advance political agendas, bypassing the role of parents. And thus you have the question being posed, should the President be allowed to address the schoolchildren of the nation over the heads of their parents?
Truly, it is astounding that anybody could object to such an act, but there it is. You might consider that paranoid or you might consider it further proof of the dangers of socialism. But wherever it comes from, it doesn't come from racism.
Of course, if Obama wants to lay this all to rest, he can give a conventional inspirational speech to the children, avoiding the code words that inflame ideological suspicion. But I'm guessing he won't. In his own liberal way, he's as arrogant as any religious fundamentalist. Both refuse to see that others might object to their characterization of their opponents or to their definitions of what is the common ground we all say we believe in.