WASHINGTON - Kellogg Company, a global brand and a household name in the United States, has said it would no longer advertise on conservative website Breitbart News, whose former chief executive Steve Bannon masterminded Mr Donald Trump's campaign and is now the President-elect's chief strategist.

Under Mr Bannon, the website had turned into a platform for the so-called "alt right" movement, which critics maintain actually stands for white nationalist.

It was typical practice for Kellogg to make sure its ads "do not appear on sites that aren't aligned with our values as a company", its spokesman Kris Charles told the Associated Press.

But the Breitbart News website retaliated with a boycott call with the hashtag #dumpkelloggs. In two days, the campaign gathered a quarter million signatures. People filmed themselves dumping Kellog cereals in trash cans and down toilets. One blew up a Kellogg product and put the video on Youtube.

Meanwhile, at an election post-mortem at Harvard University's Kennedy School, what was supposed to be a reasoned discussion of the election spiraled into a bitter shouting match between top Republican and Democratic Party aides.

Mr Bannon himself has rejected the white nationalist label, saying he is an economic nationalist. But he remains a divisive figure and was at the centre of the furious recriminations at the discussion at Harvard.

America remains starkly polarised, and it is likely that Mr Trump's call for unity at his opening "thank you" rally in Cincinnati, Ohio, on Thursday (Dec 1) has cut little ice.

And there is serious worry among activists, over how the political mood has infected schools. If adults are angrily dumping Kellogg's cereals, can their children fail to pick up on the mood?

They have certainly not been immune.

Fights over whose parents voted for whom; the bullying of girls; the appearance of swastikas and confederate flags; and talk like "Go back to Africa'' and "Go back to Mexico'' are some of the language emerging in schools across the US since the Nov 8 election.

Ninety per cent of over 10,000 teachers, counsellors, administrators and others who work at schools reported that their school climate had been negatively affected since the election, according to a survey by the anti-hate advocacy group Southern Poverty Law Centre (SPLC).

Eighty per cent described "heightened anxiety and concern on the part of students worried about the impact of the election on themselves and their families".

Four in 10 had heard derogatory language directed at "students of colour, Muslims, immigrants and people based on gender and sexual orientation"; "half said that students were targeting each other based on which candidate they'd supported", said the SPLC report released on Nov 29.

One middle school teacher in Indiana reported "white students telling their friends who are Hispanic or of colour that their parents are going to be deported".

An early childhood teacher from Tennessee reported that even though her students were from educated middle class families and culturally diverse communities, one Muslim girl clung to her kindergarten teacher after the election and asked, "Are they going to do anything to me? Am I safe?"

A middle school teacher in Oregon reported that ''My African-American students are refusing to work with the white students who supported (Donald) Trump. Students are no longer looking at each other as people, but are looking at them as who their parents supported.''

"The dynamics and incidents these educators reported are nothing short of a crisis and should be treated as such,'' the SPLC said.

Speaking to reporters at the release of the report, DC Ms Randi Weingarten, president of the 1.6 million-member American Federation of Teachers, said: "In order for our children to survive, to grow, to thrive, they have to feel safe at school and feel their parents are safe."

"Since this election, more and more of them do not feel safe."

Ms Gloria Pan, a national campaign director for gun safety, child nutrition and environmental health, for the over million-strong network MomsRising.org, told The Straits Times: "We are extremely concerned because public schools are truly one of the most important foundations of American democracy.''

"It's where all our different communities get together, and we can't afford as a nation to see our schools become so divided."

But she cautioned that the divisions were not necessarily truly reflective of America.

"There is no question that divisiveness has gone up'' she said. ''But there are a lot of people who are saying if you voted for Trump you must be a racist. I don't like to go down that road, I don't think it's true.''

Activists have also cited another worrying study on the ability of school students to distinguish genuine information from propaganda in the online environment.

A new study of school students by Stanford University researchers, led them to conclude that students had difficulty telling fake news from real.

"At present, we worry that democracy is threatened by the ease at which disinformation about civic issues is allowed to spread and flourish," the researchers said in the study titled Evaluating Information: The Cornerstone of Civic Online Reasoning.

In the study, high school and college students in 12 states were asked to evaluate Tweets, comments and articles. More than 7,800 responses were collected, and researchers were "shocked" by how many could not effectively evaluate the credibility of information.

The students displayed a "stunning and dismaying consistency" in getting repeatedly duped, the researchers said - for instance in telling fake from real accounts, and distinguishing activists from neutral parties, or advertisements from articles.

"Many assume that because young people are fluent in social media they are equally savvy about what they find there," the study noted. "Our work shows the opposite.''