DELICIOUS: A Double Stuf Oreo like the ones that were used in the science project.

Sometimes, the tiniest thing can go viral.

Like a cookie.

A mum in the US city of Lower Merion, near Philadelphia, learned that this week, after her Twitter rant over a school permission slip became part of an online debate about schools, food, and parenting.

"Insanity. I have to sign a permission slip so my middle schooler can eat an Oreo," wrote the mom, who identifies herself online only as Main Line Housewife.

The message was soon posted on various websites and parenting blogs. So was a photo of the permission slip, sent home to explain a hands-on science activity that involved Double Stuf Oreos.

The reaction surprised the mother, who declined an interview request from The Philadelphia Inquirer or to be identified by name. It also prompted the Lower Merion School District, which has no policy requiring permission for students to have snacks in class, to defend the Welsh Valley Middle School teacher, Darlene Porter.

"It's one teacher who was really trying to do her due diligence, quite honestly," school district spokesman Doug Young said Friday, noting that there are students in the class with gluten allergies.

Porter did not respond to an email seeking comment on Friday.

A sixth-grade teacher at the Narberth school, she sent home the slip this week in preparation for a lesson about the Earth's plate tectonics.

Porter planned to use the Double Stuf Oreo "to simulate the 3 types of plate boundaries and the geographical features that are created," according to a copy of the slip.

"The students may eat the OREO after the investigation if this is okay with you," the form said. "The students do NOT have to eat the OREO if they do not wish to do so."

The back of the permission form included a photo of a Oreo package, the cookie's ingredients, and a list of the nutrition facts.

Parents of children in Porter's class were asked sign the form and send it back to school by Wednesday. The activity was scheduled for Friday.

"My child - has permission to eat the OREO after the science investigation on 3/27/2015," the form said. "Without a signed permission slip, my child understands that he/she will not be able to sample the OREO."

The mother's online posting about the permission form attracted hundreds of retweets and comments, and fed into a growing debate about how schools should handle food allergies.

Columnist and reality television show host Lenore Skenazy, who founded the "free-range kids" movement to combat overprotective parenting, reposted the Lower Merion permission form on her blog. She called it "proof that we can never underestimate ... how far our obsession over child safety can go."

Others defended the teacher.

"As a food allergy parent I appreciate this," said one commenter on Skenazy's blog. "I want to know what food if any is in my child's classroom."

The Lower Merion mom, who uses the Twitter handle @mainlinewife, wrote that she did not blame the teacher for sending it.

"I blame our crazy culture," she tweeted.

While permission slips are typically needed for off-campus field trips, Young said this was the first time he had heard of a teacher sending out permission slips for a classroom activity.

But he applauded the teacher's thoughtfulness - especially because many students have food allergies. Welsh Valley, along with other schools in the Lower Merion district, already keeps students' food allergies on file, he said.

One of the students in the Welsh Valley sixth-grade class has an individual allergy plan requiring parental notification if there will be food in the classroom, Young said. But sending a permission form to all parents was an extra step that was not required.

The Pennsylvania School Boards Association advises schools to have management plans in place for specific students with allergies, said spokesman Steve Robinson. Under that policy, teachers would already know whether a student can have a particular snack.

- The Philadelphia Inquirer