Ultra-Orthodox Jews have staged one of the biggest protests seen in Israel, to demand their children be educated separately from other Israelis.
Police said 120,000 Ashkenazi Jews rallied in Jerusalem and near Tel Aviv.
They turned out to support parents who refused to let their girls share classrooms with Jewish pupils of Sephardic or Middle Eastern descent.
The protests were triggered by a court ruling sentencing some 80 Ashkenazi parents to jail.
The parents face two weeks in jail for contempt of court and were due to start their sentence on Thursday.
'Court is fascist'
The Ashkenazi parents, who are of European descent, want segregated classrooms because they say Sephardi families are not religious enough.
Some 100,000 protesters marched through Jerusalem with the 40 couples, who planned to hand themselves over to the police in compliance with a Supreme Court ruling.
About 10,000 police officers were mobilised in the city.
Marchers brandished placards and banners. "The Supreme Court is fascist," one poster read.
One protester, parent and rabbi, Meir Elmaliach, told the crowd from a makeshift stage: "We are strong because God is with us."
A similar protest in Bnei Brak near Tel Aviv drew about 20,000 people, said police.
The families at the centre of the legal battle come from a strictly observant sect of Hasidic Jews called Slonim, who have Ashkenazi lineage.
'Not a drop of racism'
They have pulled their children out of Beit Yaakov girls' school in the West Bank settlement of Immanuel, and set up lessons elsewhere in the area.
The Slonim parents say their objections are based on differences in religious observance between the Ashkenazi and Sephardi traditions.
Yakov Litzman, an MP from the ultra-Orthodox Ashkenazi party, United Torah Judaism (UTJ), told army radio there was "not a drop of racism" in the parents' decision.
"There is a set of rules [in the ultra-Orthodox community]. We don't want televisions in the home, there are rules of modesty, we are against the internet," Mr Litzman was quoted as saying by AFP news agency.
"I don't want my daughter to be educated with a girl who has a TV at home."
The court had given the parents until Wednesday to send their children back to school, but they refused.