BERKELEY — A school district plan to add portable classrooms at Thousand Oaks Elementary School will require a city election, according to a novel legal challenge by a group of school parents opposed to them.

The 2.6 acres of land surrounding the school, including a playground and adjacent park, is city land according to city law and agreements between the city and the school district, the parents say.

What’s more, the parents say, city law requires an election to build anything on that land.

Berkeley City Attorney Zach Cowan is seriously considering those arguments made in a 20-page letter to his office by Thousand Oaks parent and attorney Nancy Hamill and parent Cliff Young. Hamill said the claims in her letter could form the basis of a lawsuit against the school district if it proceeds with the plan for the 2016 school year.

Cowan said he will make a determination on the parents’ claims soon.

Hamill and her husband, Patrick Hamill, who is a vice president of the school’s parent-teacher association, and Young are opposed to portable classrooms because they say they are cramped, “depressing” and not a suitable environment for learning.

“It would be wise to pull this off the table,” Hamill said. “I don’t want to have to sue them to do it. I don’t think any kids should have to go to school in a portable. We should be setting a higher standard for education for crying out loud. The district should be thinking creatively. They are public servants and they are not doing their jobs.”

The letter references city law that designates public school playgrounds as public parks, which cannot be used for other purposes “without the Berkeley City Council first having submitted such use to the citizens.”

Berkeley schools spokesman Mark Coplan said Hamill is wrong about the park issue.

“They believe the city owns that property, but they don’t,” Coplan said. “A portion of it is city park, but it’s not the playground. The fact that they are raising that issue doesn’t make it so.”

Coplan said portable classrooms are “quite common” across the country and are not as bad as Hamill contends.

“Hopefully, in a couple of years this enrollment bubble passes and we won’t even need the portables,” Coplan said. “It’s looking that way right now, and if in the next six months we get larger numbers enrolled and it tells us something drastically different, then we have the option to continue with the portables.”

The school board must, however, decide by next Wednesday’s meeting whether to spend $188,000 on an architect to begin planning for portables at Thousand Oaks, LeConte and John Muir Elementary schools. Architects need 18 months to plan and design placement for the portables.

Berkeley Federation of Teachers President Cathy Campbell said legal arguments aside, portables are not as bad as Young and Hamill say.

“Portables have a lot of advantages,” Campbell said. “They have their own cooling and heating systems. The new ones have better lighting and more windows. Sometimes their shape is less than ideal, but a lot of our current classrooms are not necessarily big enough either. As a union we wouldn’t say these are horrible teaching and learning conditions. It’s just not the case.”

But Thousand Oaks parent Trevor Redman, who was watching his son and a friend play basketball after school recently, doesn’t like the idea of portables.

“I know they need more room, but there’s not much space here,” Redman said. “Where would you put them? I don’t agree with portables. They don’t need to have them here.”

Contact reporter Doug Oakley at 925-234-1699. Follow him at Twitter.com/douglasoakley.