Diversity — altogether good? Let me gently prod you on that.

"Diversity is our strength" is a popular affirmation today. It's the default "correct" view to hold in the Western world — to welcome immigrants and embrace the rich mixing of races and ethnicities, to be open-minded and tolerant.

The celebration of diversity adorns bumper stickers, is proclaimed by progressive politicians, and is rampant in today's advertising and entertainment.

Of course, the truth is more nuanced.

Diversity can be a challenge and a problem.

Observe the various ethnic groups in many cities — how they concentrate in their own neighborhoods. It's as if there were a collective understanding that to disperse, while diversifying the population as a whole, would be like spreading embers about a hearth. Uniformity, homogeneity is what fuels the blaze of culture.

All cultures are collections of common customs, practices and beliefs that hold groups of people together. It is because many different peoples throughout history have coalesced to ignite distinct cultural flames that we have the opportunity for diversity in the first place — instead of one undifferentiated mass of universal sameness.

So uniformity, too, is necessary and good, if only as the foundation for diversity. Just don't go driving around sporting a "Uniformity is Our Strength" bumper sticker.

White Americans have largely shaped the default national culture, with large contributions from African-Americans and other racial and ethnic groups, by diluting and letting go of specific ethnic identities and their idiosyncrasies (Irish, German, Italian, etc.). Yet at least in cities where they now find themselves a minority, whites who practice the same religion or share traditions and customs also find that uniformity is a strength, especially when seeking to preserve a specific heritage (Russian, Greek, Jewish, etc.).

That "diversity is our strength" fails to tell the whole story became clear to me recently when I was teaching at the Hmong International Academy in Minneapolis. I stepped in to fill the need for a gym teacher at this Hmong-focused charter school on the city's North Side.

This area's Hmong community founded the K-8 school some years ago. It began with an exclusively Hmong student population; the school celebrated Hmong events and taught the language. The community built a strong school, and soon, despite the cultural focus, many non-Hmong families in this diverse part of town wanted to enroll their kids.

After some years of this trend, the school today is roughly half Hmong, half non-Hmong, according to two staff members who talked with me about their school.

This division was evident in gym class. For each grade I taught, two classes arrived. One was the Hmong language immersion class. The other was taught in the standard English curriculum. One class was all Hmong kids; the other was a mixture, but almost all non-Hmong. These two distinct single file lines approached the gym door.

Despite being on its way toward losing a Hmong student majority, this school has maintained its identity through the language immersion program and considerable concentration of its Hmong students. The school now seeks to balance homogeneity and diversity. That balance was put to the test later that day at the school's annual Hmong New Year celebration.

All the grades crowded into the main gymnasium, along with parents arriving to watch their children perform. Hmong students from kindergarten to middle school wore traditional, brightly colored costumes and performed Hmong-inspired songs and dances.

But clashing with the festive atmosphere was a general disinterest from many other students. During the performances, many of the younger non-Hmong students became fidgety, restless. Older students not dressed for the occasion chatted and paid little attention.

This apathy was loudest during an uncomfortably silent performance. A middle school class of Somali, black and other groups stood expressionless on the risers as their teacher tried to conduct them in a choral number. I kept waiting for the piano intro to end so the singing could begin. The intro had ended long before I realized these kids were simply waiting out these three or four minutes of awkwardness.

I flashed back a few years, to a period when I worked at a Hmong-focused charter school in St. Paul, Community School of Excellence. The cultural New Year celebrations at that school were all-day affairs, during which literally every student and staff member wore a traditional ethnic outfit. I still have my Hmong vest and necklace from those days.

The difference between the two schools? More than 90% of the St. Paul school's student population was Hmong. And even the other 10% were a unified group from the Karenni community, who on these occasions were also able to dress traditionally and perform their cultural songs and dances.

At the north Minneapolis school, with its diverse population, there was no way for a cultural tradition to inspire such unifying enthusiasm. Their celebration suffered a reduction in volume, brightness and overall impact.

This is going to sound like heresy to some, but in that situation it would have been accurate for those involved to say: "Diversity is our weakness."

I voice this heresy as someone who has resided for extended periods in China and Tanzania to immerse myself in other worlds. I've experienced unfamiliar cultures from Southeast Asia to Latin America. Here in the U.S., I've loved walking the streets of New York City just to people-watch the rainbow of urban America.

And right here in Minnesota, I've learned much from contact with the Hmong, Somali, Latino and Native American cultures.

Yet diversity is our strength only when balanced with adequate commonality. The energetic, dazzling St. Paul school event resulted from common ground and shared traditions, a foundation upon which the 1,000-member school population could unite as a distinct community.

And the only reason an outsider like me has been able to enjoy and learn from such unique and mind-expanding events — at school celebrations and in cultural settings around the world — has been because, in every case, I was one of the few outsiders present.

Cultures, by definition, differ in beliefs and values. Culture often overlaps with race. Cultures don't include and accept everyone. Discomfort with such truths has led to our abandoning nuance on this taboo topic. It's safe only to intone bumper sticker slogans: Diversity is our strength, period.

Meanwhile, if that north Minneapolis school loses much more of its critical mass of Hmong students, the beauty of that cultural identity in that school will fade away. The embers will be too scattered to create a blaze.

Maybe that's just the price we must pay for living in a diverse country like the U.S. This isn't China or Tanzania. This is a multicultural nation where soon literally every citizen will be part of a minority group. There is no typical American. Yet there is an idea of "America" that transcends race and ethnicity.

Laws and ethical considerations already dictate the need to treat all school applicants equally. But a potential landmark lawsuit making its way through the Minnesota courts (Cruz-Guzman v. Minnesota) could compel racial diversity in schools regardless of who applied where.

The lawsuit effectively argues that racially lopsided schools in the seven-county metro area should be prohibited. Specifically addressing a handful of culturally based charter schools, advocates believe diversity is such a strength they would tell the Hmong community it is illegal for them to have a school like the one they have in St. Paul. All this, according to the ACLU of Minnesota, is done in the name of defending the "educational environment for racial- and ethnic-minority students."

Another irony — but hopefully not a tragic irony — is that the Minneapolis Hmong school's energizing ethnic identity is key to the strength that makes the program attractive to non-Hmong families. Hopefully, this is a model for balance, an equilibrium: A strong cultural institution that also serves many other groups in the community, a blend of homogeneity and diversity.

It wasn't lost on me that the principal at this school was a black man. And it was heartwarming to see a young African-American student in his Hmong clothes, joyfully dancing. He was experiencing something he'd never have known were it not for the existence of this school and its community. I understood his delight; I've been there.

These paradoxes of uniformity and diversity are part of American life — and increasingly familiar around the world. We're better served leaving the absolutes to bumper stickers and braving the nuance needed to secure that which we claim is our strength.