The parents of 43 ultra-Orthodox girls were tonighton their way to prison for two weeks today after defying a court order over their children's schooling that has highlighted the division between Israel's religious and secular communities.

More than 100,000 ultra-Orthodox men marched through Jerusalem to show their support. "They are going to jail with joy," said Barry Dubin, 28. "We ultra-Orthodox parents will not cave in to the courts."

The parents are Ashkenazi, originating from Europe, and are in a long-running battle to have their daughters educated separately from Sephardi girls originating from north Africa and the Middle East.

They reported to a police station this evening, according to a police spokesman. The mothers and fathers were being sent to separate jails to serve their sentences. Jerusalem's centre was gridlocked as a result of the march. Police were standing by in the city's Jewish religious areas last night, the spokesman said.

The relative scale of the demonstration, for a city whose Jewish population is half a million, was enormous. Another demonstration in Bnei Brak, near Tel Aviv, attracted thousands more.

The reason for wanting separate education, the parents claim, is not racism but a desire to remove their daughters from the influence of those they consider less strict in their religious observance. Watching TV at home, having access to the internet, and a laxer dress code among the Sephardi ultra-Orthodox have been cited.

The ultra-Orthodox school in the illegal West Bank settlement of Immanuel segregated the girls, a move that was subject to a legal challenge resulting in an order to reintegrate. The parents of the 43 girls refused to send them back to mixed classes, leading to sentences for contempt of court.

Underlying the case is the rejection of what the ultra-Orthodox community's sees as state interference in their religious practice and life. "We don't give our girls all the knowledge that there is in the world," said Esther Bark, 50, a mother of seven daughters watching the male-only demonstration today. "We shelter them, and that's why they need a sheltered school. We can't mix a whole assortment of girls in one school."

As police helicopters throbbed over the mass of black-hatted demonstrators, Aaron Shuv, 28, said: "We only follow the rules of God. The Torah [scriptures] is above all government."

The issue had nothing to do with discrimination, said Dubin, a father of two. "No court in the world should have the right to tell me how to educate my sons or daughters. The court went against our rabbis."

Jerusalem's ultra-Orthodox community has swollen to a third of the Jewish population, assisted by a high birthrate and departure of thousands of secular residents. The secular population is increasingly resentful that its taxes support welfare benefits for the ultra-Orthodox, who reject paid work in favour of religious study.

The political leverage of the ultra-Orthodox has also increased since the election resulted in a coalition dependent on the support of small religious parties.

"The ultra-Orthodox community is getting stronger and stronger," said Yitzhak Brudny, a political scientist at Jerusalem's Hebrew University. "The tensions between the religious and secular communities have become especially pronounced. It's both a class war and a cultural war. The ultra-Orthodox are dirt poor. Among secular Israelis and moderate Orthodox Jews, they are seen basically as parasites. And they have no desire to integrate with other communities."

Secular Israelis were enraged by the ultra-Orthodox refusal to abide by the law on the schooling issue.

"For many years the culture war has hung over us like a dark cloud, like a threat," Yossi Sarid, a former member of the Knesset, wrote in the Ha'aretz newspaper. "Now it is happening; the war has erupted. The great Haredi [ultra-Orthodox] rebellion has begun and is raging on several fronts … It will destroy basic values, without which a democratic, developed state cannot exist. It will be lost unless it fights back."