Republicans Steve Lonegan and Alieta Eck are running for the GOP nomination in the August primary.
The divide on schools is one of the most stark disagreements among the Democrats vying to replace the late Sen. Frank R. Lautenberg.
"Kids born in urban areas, unless they get lucky and get to a magnet school or private school, live in American apartheid," Booker said, adding, "The zip code you're born into will greatly determine your outcome."
He said charter schools have helped Newark.
The other candidates said charters can help, but traditional public schools will reach far more students.
Test scores at Newark's charter schools in many cases beat New Jersey averages, but the traditional public schools, controlled by the state, still lag.
"The solution will not come through turning education into a market-based enterprise with vouchers, with treating teachers as a means of production and students as commodities," Holt said. "The emphasis has to be public schools, publicly funded."
Pallone, too, worried about a drain on funding from charters and vouchers, and that private interests backing charters could gain too much control. He also called for more spending on public schools.
Oliver took a similar stand, saying most students still attend traditional public schools and called for less "federal intervention" in schools. "Every state is different."
Booker took fire over his decision to skip a Saturday debate later broadcast on ABC.
"I, fortunately, still am running a pretty large city," Booker said, adding that at the time of the debate, he was in Newark for the opening of a business.
"Your campaign said you were at a barbecue in Belleville," Pallone shot back.
And while Booker noted that he will participate in the next two debates - the same number held when Lautenberg, who was a Democrat, last faced a primary challenger - Pallone said "the voters in this shortened time frame need to have more knowledge about what we stand for." A special election in October was called by Gov. Christie after Lautenberg's death in June.
The candidates all denounced what they called the corrupting influence of outside money in politics, even as independent expenditures are starting to flood their race.
Pallone has asked the other candidates to sign a pledge to reject such outside groups, and pointed out that no one joined him.
He and Holt both took shots at Booker, who is getting support from a super PAC called the Mobilization Project. The group has raised nearly $80,000 to fend off attacks from the American Commitment Action Fund, a conservative group that has raised $100,000 to target Booker.
Booker called outside money a "toxin" that has turned elected officials into "full-time fund-raisers," even as he admitted that he has had to bring in large sums to "prevent ourselves from being taken down."
He would not disavow outside aid, "not when I have super PACs attacking me from the other side."
Booker said a hotel magnate whom he did not name was interested in spending millions in the next two weeks to "snuff him out" of the race.
Booker has a huge fund-raising lead, having brought in $6.5 million in the first half of the year. He also is the heavy favorite in public opinion polls.
The Newark mayor highlighted his role as a city leader in his push to join the Senate, saying he would fight for hard-hit cities such as Camden and Paterson, as well as Newark and others around the country.
"We are not creating a nation of liberty and justice for all," he said, pointing to the plight of the urban poor.
He said only 20 mayors have ever gone directly from city hall to the Senate and said, "We are lacking that experience, that expertise and that vision."
Holt argued for supporting cities with revenues from wealthy areas.
"There has to be some shift of revenues from the wealthy parts of New Jersey to the urban areas," he said.
Oliver and Pallone called for more federal investment in cities.
Pallone argued that stimulus dollars, for example, helped cities avert layoffs after the recession.
Contact Jonathan Tamari at phillynews.com or follow on Twitter @JonathanTamari. Read his blog 'Capitol Inq' at www.inquirer.com/CapitolInq.