MENLO PARK -- A fire early Thursday ripped through a the main building at a private school on the Peninsula, destroying a third-grade classroom and several administrative offices.

The fire at Beechwood School was reported at 3:52 a.m., Fire Inspector Jon Johnston said. One of the school's buildings is a total loss, with a damage estimate of $300,000.

Johnston said a passerby called 911 to report seeing smoke coming from the school. Firefighters arriving at the school determined there was a potential for the roof to collapse, so they battled the blaze from the outside, Johnston said.

During the fire, the roof did collapse. It took firefighters about two hours to bring the fire under control, and just before 8 a.m. they were still extinguishing hot spots, Johnston said.

Principal David Laurance said the fire consumed Building 1, which housed all of the administrative offices, as well as the third-grade classroom.

Laurance said he received a wake up call from fire officials at about 4:30 a.m. and rushed down to the school. When he arrived he saw lots of smoke and flames shooting through the roof.

"It was clear it was a pretty serious situation," Laurance said.

No other classrooms were affected by the blaze.

"The way our campus is our together it's pretty unlikely it would spread," Laurance said. "I was mostly thinking about that one building."

Laurance said the school will shut down for two days and

He said he was told by firefighters it is unclear how the blaze started. Johnston said an investigation into the cause of the fire was expected to begin later Thursday.

Laurance's most immediate challenge is to find a temporary space for the 18 third graders whose room was destroyed in the blaze. He is also worried about the "emotional toll" the students may experience.

Laurance also notes that the third-grade teacher lost all of her classroom materials in the blaze.

"She's really outstanding, pouring her heart and soul into it and the amount of time she's out into it, " Laurance said. "It's got to be hard for her to think about, losing everything she's collected and created. "The idea of starting over is pretty overwhelming."

As firefighters worked to put out smoldering hot spots, Anna Hodges and her 10-year-old son Tiere watched from a street behind the school.

Tiere, now a fifth-grade student at Beechwood, spent his third grade year in the fire-ravaged building.

"It makes me sad," Tiere said. "I had a lot of good memories in that classroom. One of my favorite teachers works in that classroom and it's sad to see it go away like that."

Anna Hodges said the fire will likely cancel a back to school picnic planned for the weekend and delayed an exciting field trip scheduled today for fourth and fifth-grade students.

Tiere said students were to visit a Redwood City company to learn about starting their own business. Tiere said students were going to make friendship bracelets and sell them for fake money.

Anna Hodges said she is sad to see Beechwood's main building destroyed but believes the family-oriented school will be OK.

"Its going to take some time but I'm sure we'll bounce back," Hodges said.

Tiere wondered about how the fire started. He said vandals recently broke into a gym coach's office and spray painted the walls.

"I'm hoping no one did this," his mother said. "If they did it's just sad."

Gibby Smith, 25, came down to the school first thing Thursday morning after hearing his daughter's school was on fire. Smith's daughter, Danae, is a kindergarten student at Beechwood.

"She loves school and going to school," Smith said. "For her it's really sad. She had the sad face on. But she'll be able to return on Monday."

Contact Mark Gomez at 408-920-5869. Follow him on Twitter @MarkMgomez