Five middle school boys from San Mateo County face felony charges in connection with the attempted rape of two classmates during a March field trip.

The alleged attack happened in Stulsaft Park while 20 John F. Kennedy Middle School students were there as part of a social studies lesson on March 4. The two girls who leveled the allegations, both 12-year-old seventh-graders, broke off from the group at some point and were allegedly followed by the defendants, said District Attorney Steve Wagstaffe, who declined to release further details.

“The shocking part is the age of the minors accused in this crime,” said Wagstaffe, adding the defendants are all between 13 and 14 years old. They were arraigned Monday on charges that include assault with intent to commit rape, sexual battery and lewd acts on a child.

The Redwood City School District, which has 16 schools and 9,000 students, has begun an investigation of its policies and staff in response to the incident, said Jane Yuster, director of student services.

The students were accompanied by two adults — a teacher and a teacher’s aide — which meets the district field trip policy of one chaperon for every 10 students. The children walked the short distance from the school to the park on the day of the excursion.

School officials plan to hold a hearing on whether the boys charged in the alleged attack will be expelled.

“They aren’t allowed back into school until all of this is resolved,” she said.

The students on the trip ranged in age from sixth to eighth grade. All were part of a voluntary program in the district that shores up the English skills of students who have been in the United States for less than a year.

The school first got word of the investigation on Wednesday, the second-to-last day of school for the year.

One of the girls revealed the attack to a school counselor, who subsequently contacted police. Officers arrested the boys the same day.

Yuster said police have the boys in custody and the school has been in close contact with the alleged victims and their families.

“Suffice to say we are very concerned about this,” Yuster said. “That’s the best we can do, understand what happened.”

Contact Joshua Melvin at 650-348-4335.