Manhattan —

A boy wore a placard around his neck reading, “I am Trayvon Martin.” Others waved posters of the slain Florida teen, emblazoned with the words, “Protect Our Children.”

They were among 2,000 demonstrators who rallied March 21 in Union Square, in what organizers called the Million Hoodie March – a reference to the garment worn by the 17-year-old high school student the night he was gunned down. Protesters, many of them parents, called for justice for Trayvon Martin – and demanded protection for their own children.

“I just want my kids to understand what’s going on now,” said Bronx mom Taisha Herrara, who brought her children, ages 6 and 7, to the rally.

Her sentiments and those of much of the crowd were echoed two days later by President Obama, who declared at the White House, “If I had a son, he would look like Trayvon.”

The Union Square rally featured speeches by City Council members Jumaane Williams (D-Brooklyn) and Ydanis Rodriguez (D- Manhattan), who spoke against gun violence and racial profiling. But the gathering’s emotional high point came when Trayvon’s parents, who traveled to New York for the event, spoke.

“This is not a black or white thing,” said Sybrina Fulton, Trayvon’s mother. “This is a right and wrong thing.”

Florida authorities said they will convene a grand jury next month to probe George Zimmerman, 28, the self-appointed neighborhood watch leader who admitted to shooting Trayvon on Feb. 26. Sanford, Fla. police have come under fire for failing to charge Zimmerman and thoroughly investigate the shooting.