The group, led by their teacher Sabeth Schmidthals, counted 20 high school students, the majority of them Muslims, the broadcaster said.
"These are very active students," Schmidthals told Deutschlandfunk. "They go against the popular belief that youngsters or Muslim students are not interested in this topic."
"I was spat on by a man in the street who then ran away", Sheida Nur, one of the girls in the group, told German radio.
She and three other girls wearing hijab were the main targets of racial slurs and threats.
Nur also said that police officers were idly standing by and did not offer protection during the abuse.
"We saw the policemen grinning. Then a Polish man explained that the police would not want to help us," one of the boys in the group said.
Another girl was expelled from a shopping mall, allegedly for speaking Farsi in a phone call to her brother.
"They came up to me and asked me to leave. They said I was disturbing the people. I asked why. Just because I was talking in Farsi and I was a foreigner? They said 'yes'."
Another girl had an encounter with a woman who "came at us yelling 'go away'. She then poured her drink on me and my camera," she told Deutschlandfunk.
In a market in the city of Lublin, the girls wearing hijab (the hijab is a headscarf worn by many Muslim women who feel it is part of their religion) were turned away from a stall where they tried to buy water, allegedly because they were not Polish.
In another incident, one of the girls was reportedly threatened by a man with a knife. "I thought he wanted to ask me something, but then I ran straight back to the hotel."
Polish police, responding to a request from the BBC, said that there was no complaint filed in connection with these incidents and that review of security footage showed "no incidents involving foreigners".
No Muslim refugees
The organisers of the school trip, Haus der Wannseekonferenz, have expressed concern in the wake of the allegations and promised to take the matter up with their Polish partners.
A letter will also be sent to the Polish ambassador to Germany, according to Haus der Wannseekonferenz director Hans-Christian Jasch.
The group had visited the sites of World War II concentration camps in Treblinka and Maidanek in order to learn more about the suffering of Polish civilians under Nazi occupation.
The Polish prosecutor's office told the BBC that the number of hate crimes against Muslims had doubled from 2015 to 2016.
Poland's conservative government refuses to take in Muslim refugees claiming they would not fit in a majority Christian Catholic society.
During the peak of the refugee crisis in 2015, Education Secretary Jaroslav Gowin said, "every (…) people has the right to protect itself from extinction".
Source: Al Jazeera and news agencies