The children who recited a violent poem in Arabic and performed choreography to a song referencing the “blood of martyrs” last month at a North Philadelphia mosque did not understand the words’ meaning, and the volunteer aide who made those selections has left the private academy based there, according to a statement released Wednesday by mosque and school leaders.

Officials of the Muslim American Society (MAS) in Philadelphia and the Leaders Academy learning center say that other aides at the April 17 celebration of Umma (Arabic for “community”) Day did not know the language, and that those who did were not paying attention to the lyrics during what was a hectic event. They called the performances “a grave mistake” and “ours to own.”

The statement is the latest turn in a controversy that began to roil after video excerpts of the students’ show — one youngster mentions chopping off heads to “liberate the sorrowful and exalted Al-Aqsa Mosque” in Jerusalem, a holy site for both Muslims and Jews — were posted by the Middle East Media Research Institute (MEMRI), a monitoring group.

“We are deeply saddened to have hurt our partners in the Jewish community and beyond,” the statement read.

Mosque and academy officials also apologized to the local Muslim community, within which some institutions have reported “hate calls and death threats” since the video was posted. Protests have been held outside MAS Philadelphia. Speaking on condition of anonymity, a parent of a student in the video told The Inquirer that her child had been the subject of “hate letters” and was nearly beat up.

Nancy K. Baron-Baer, regional director of the Anti-Defamation League in Philadelphia, said she appreciated the apology and explanation.

“We understand that mistakes can happen,” Baron-Baer said. “However, the fact that children and adults did not understand what they were saying is neither an excuse nor proper pedagogy. It should be incumbent on the adults in the room to understand what is being said before agreeing to perform the songs and poetry. It is also important to recognize that words like the ones said are unacceptable in any language and at any time.”

The songs and poem were chosen to highlight the students’ ability “to read and project Arabic rhetoric,” but the children had not yet “mastered enough grammar to comprehend the words,” the statement said. The former aide had selected some songs with Palestinian themes because the Islamic center has a large Palestinian community. The song referencing the “blood of martyrs” and the return of “our Palestine” — popular on YouTube, according to the statement — was playing on a computer in the background as the children performed.

The national Muslim American Society said in an earlier statement that the two-hour Umma Day event, meant to celebrate the school’s diversity, had not been “properly vetted” and that the recitations were “an unintended mistake and an oversight.”

The Leaders Academy is described as an independent organization based at MAS Philadelphia, which is also known as Al-Hidaya Mosque/Masjid. It rents space at the mosque and offers K-12 students who use the Pennsylvania Cyber Charter School curriculum a place to complete lessons with the help of volunteer aides, said Timothy Welbeck, a lawyer for the Philadelphia branch of the Council on American-Islamic Relations (CAIR).

MAS Philadelphia was founded in 2003. At least one official of the mosque previously held a similar post at the Leaders Academy, but “I don’t believe” the mosque official is still part of the learning center, Welbeck said.

In addition to forming an advisory council to monitor and review operations, mosque and Leaders Academy officials participated in a training session on Judaism and anti-Semitism on Saturday as part of an effort to insure that similar incidents are not repeated there, the statement said. Jacob Bender, executive director of CAIR Philadelphia, led the training.