I went to high school in the 1970s in Montgomery County. The district was overwhelmingly White then, with a small number of African-Americans.

That’s not the case any more. Today, just under 40 per cent of county residents are White. About one fifth are Hispanic, one fifth Black and 15 per cent Asian. One third of the population was born outside the United States, and 43 per cent speak a language other than English at home.

Montgomery has also become the most religiously diverse county in America, according to the Public Religion Research Institute. Muslim mosques sit next to Buddhist and Hindu temples, and a wide variety of Christian churches, including Seventh-day Adventist and Jehovah’s Witness. One county road boasts so many houses of worship that locals call it the “Highway to Heaven”.

But that also means that the citizens of Montgomery County are more likely to disagree with each other, especially on matters closely tied to faith. And if you’re the kind of liberal who displays a “Celebrate Diversity” sticker on your car — or a Pride flag over your door — you might have to admit that some strands of this glorious rainbow might not see the world the same way you do.

That’s the big takeaway from the Supreme Court decision on Friday in Mahmoud v Taylor, which allowed Montgomery County parents to opt their children out of elementary-school lessons involving several LGBTQ+-themed storybooks. The lead plaintiffs in the case are Muslim parents who objected to the books, which included stories about two men getting married and a transgender child who wants to identify as a boy.

I applaud the school district for trying to teach young children that there are many kinds of people, relationships and families. But I also realise that among these many kinds of people are some — especially those who came here from other countries — who view gender as immutable and sexual behaviour outside straight marriage as a sin.

In other words: diversity can be conservative.

It took me a while to get there. Several years ago, I embarked on a book project about the history of sex education in public schools. I knew the subject was controversial across the West, and I thought I knew the battle lines: liberals of every colour against White conservatives, particularly evangelical Christians.

I was wrong. Sure, White right-wingers such as Phyllis Schlafly in the United States and Mary Whitehouse in Britain opposed sex education. But they joined hands in the 1970s and 1980s with immigrant Muslims and Hindus, who shared their distaste for curriculums that addressed abortion, contraception and — most of all — homosexuality.

Almost every media account I found about this political alliance used the same headline: “Strange Bedfellows”. We’re talking about people who disagreed about nearly everything else, including immigration. Yet they stood together in opposing sex ed.

And that put me and my fellow liberals in something of a bind. Normally, we try to welcome immigrants by deferring to their sensibilities. But on questions of sex, we were more likely to impose our own.

“The greatest effort in the Netherlands will be to make social life more sexually diverse and to create access for young people of all ethnic backgrounds and religious persuasions to erotic worlds they may be interested in,” a Dutch observer wrote in 2000, noting immigrant resistance to sex education. The challenge is “to add multisexuality to multiculturality”.

But for many people around the world, “multisexuality” is a direct challenge to their cultural and faith commitments. So if we want to live in a truly multicultural society, we may have to let parents opt their children out of lessons about gender. Most states already allow opt-out for sex education. It might be time to add other subjects — including elementary-school story time — to the list.

I realise this places a new set of burdens on teachers and schools. How will they know which families might object to which lessons? And what will the children who sit out do while the rest of the class is learning about same-sex marriage or transgender children?

But I also think these challenges can teach everyone important lessons about our nation. When some children opt out, students will learn that Americans disagree — deeply and fundamentally — about these matters. And they will also learn that we can accommodate our differences, even when it is hard.

If you celebrate every colour in our national rainbow, you also need to reckon with the cultural conservatism of many people of colour. We can’t pretend that everyone on the Highway to Heaven wants to go to the same place.

• Jonathan Zimmerman teaches education and history at the University of Pennsylvania and is the author of Too Hot to Handle: A Global History of Sex Education