GLOUCESTER, Mass. -- A spike in pregnancies at a Massachusetts high school is being blamed at least in part on an agreement made by a group of girls to get pregnant.

Time magazine quoted the principal of Gloucester High as saying the girls decided to get pregnant and raise their babies together.

The number of pregnancies at the school jumped from the usual four per year to 17. Gloucester High School has 1,200 students, reported Boston TV station WCVB.

Principal Joseph Sullivan told Time magazine that the girls were making frequent stops at the school clinic for pregnancy tests and "seemed more upset when they weren't pregnant than when they were."

He said when some of the girls found out they were pregnant, they traded high fives and talked about baby showers.

One of the fathers was identified as a 24-year-old homeless man, Sullivan told the magazine.

Students said they were shocked.

"I remember finding out one person was pregnant. That was, like, incredible ... these numbers are outrageous," student Mollie Wagner said.

"I am friends with a couple of them," Wagner said. "I mean it's their decisions -- whatever they want to do. You won't catch me getting pregnant in high school. No way," Wagner said.

Brianna Porter graduated last week. She and many other teens said that the pact story has been overstated -- that only a few girls actually made a pact, WCVB reported.

"I heard that there were two girls who were best friends and they wanted to, like, be pregnant together," she said.

The school district's superintendent said the girls who got pregnant generally "lack self-esteem" and have a lack of love in their lives.

A friend of the teens said they seemed "curious" about her own pregnancy.

Christen Callahan had her baby when she was 15. The former Gloucester High School student told NBC's "Today" show that some of the teens would ask her questions and talk about how they thought their own parents would react if they were to get pregnant.

Callahan said she tried to warn her friends.

"You lose everything," Callahan said. "You lose your friends. You lose being able to go out. I know a lot of people that like to go out every night. You can’t really do it. You lose -- you lose everything."

Callahan said she has no firsthand knowledge of any pact among other Gloucester students to have babies.