The homeless young black man walked jerkily along San Diego’s Martin Luther King boulevard, his eyes fixed blankly on the middle distance. He had draped a grey towel over his head to shield himself from the hot southern Californian sun but he was carrying a grey blanket that would ward off the cold of the coming night.

He paid no heed to either the giant billboard advertising luxury condominiums in the adjacent tower block (two bedrooms from $470,000) or the eloquent extracts from King’s speeches that were inscribed on the stones under his feet. Each one contained dire warnings of the calamities to come if racial inequalities were allowed to persist.

But this being America, a land rich in paradox, a middle-class black girl aged about 10 whizzed past him on expensive in-line skates. Beware of easy stereotypes, she seemed to say.

There had been other conflicting messages a few hours earlier in the nearby Marriott hotel when Professor James Banks of Washington University, in Seattle, had addressed the American Educational Research Association. He had also quoted King: “Injustice anywhere is a threat to justice everywhere.” Some would, however, argue that Professor Banks’s speech was a reminder of the progress America has made in the past 40 years.

Banks, an African-American, spent his childhood in the Arkansas delta in the 1950s. He could not use the public library because of the colour of his skin, neither could he drink from the white man’s water fountain. But today he is the president of one of the world’s most prestigious educational organisations.

Even so, dozens of the conference papers underlined the inequities that many African-American and Latino children still endure. Now it is poverty, rather than a black or brown skin, that prevents millions of children from sharing in the American dream, but all too often they are synonymous.

Last week the newspaper USA Today reported that parent-supporters of a 400-pupil state school in a wealthy white enclave of northern California were contributing more than $1 million a year to its funds. Their latest money-making event had been an auction where the lots had included a power breakfast with Donald Trump and a walk-on part in the latest Robin Williams film. It raised more than $100,000.

The following day Valerie Polakow, a researcher at Eastern Michigan University’s College of Education, told the AERA conference about life at the other end of the social spectrum and spoke movingly about the “toxicity of poverty”. She said that America’s new welfare laws are having a devastating effect on single mothers and are likely to increase the number of children who are living in poverty by more than 1 million.

Other researchers presented disturbing papers on violence in urban schools. One in five middle schools witnessed at least one serious violent crime - such as a rape or armed attack - during 1996-7. Even more shockingly, it said that as many as 135,000 US children took guns to school every day.

The numbers of African-American pupils who are being classified as “seriously emotionally disturbed” and shunted out of mainstream education are also alarming, as Gwendolyn Cartledge of Ohio State University pointed out. “A lot of our administrators are short-sighted,” she said wearily. “They are cleaning up the schools but making the world a mess.”

Such warnings loomed even larger than usual at this year’s conference because its theme was “Diversity and citizenship in multicultural societies”. But a bewildering range of topics that had nothing to do with that theme were also addressed by the 3,000 paper-presenters: school effectiveness, semiotics and sexuality - to name but a few.

There were also stacks of more cryptically titled papers that might have been on any - or none - of these subjects. What were we to make of “Toward a lifted theory of dismembered meanings” or “Dream girls waiting to exhale with the rainbow is enough: diversity with the essence African-American women speak”?

One American researcher flicked through the conference programme, which was as thick as a telephone book, and gasped: “I’m way over my head ... like lullaby.” That was a typical reaction to this monster of a conference that this year attracted 12,000 researchers, including a large British contingent.

As always, some questioned the point of it all. Of course it was of benefit to countless individuals - lobby conversations in the conference hotels often lead to job offers, research partnerships and invitations to collaborate on books.

But some of the research findings seemed to be either of dubious value or open to question. Is it really true that androgynous young Puerto Ricans experience less stress than their more “normal” contemporaries? And are we any better off for knowing that?

Farce was never far away either. A group of military educationists who pioneered computer-based instruction struggled to operate their overhead projector. And, perhaps predictably, no one turned up for a presentation on chronic procrastination.

Nevertheless, many papers that were ignored by the US media contained insights that could make a significant contribution to educational progress and human happiness - if only they were disseminated and acted upon.

America is a country that has always wasted much of its resources because it knows it has so much in reserve. But it surely cannot afford to go on squandering knowledge in this way, particularly if it is serious about making its education system the best in the world.