I BLAME the desks. I blame our MSPs too, of course. Don’t get me wrong, they’re bairns.

But there’s something about sitting with your pals in rows of wooden desks that takes folk back to their schooldays.

Add a debate on education, the last day of term, and a Presiding Officer who missed her vocation as a belt-flashing heedie , and some childishness was probably inevitable at FMQs.

Our parliamentarians did not disappoint. Kezia Dugdale started with a playground joke.

“Labour will protect education spending in real terms for the whole of the next parliament,” she said, when everyone knows Labour will be in opposition for the next parliament. At least.

She had a good prop, though, a 186-page budget document from SNP-run Perth & Kinross Council containing reams of education cuts, including an end to supply teachers.

“Classes may have to be sent home and possibly schools closed,” she quoted.

So why wasn’t Nicola Sturgeon raising income tax a smidge to avoid cuts?

Like the student who writes the essay they prepared regardless of the question, Ms Sturgeon said the cuts came from Westminster, and because Labour campaigned “vigorously with the Conservatives” to keep the Union, it was partly their fault.

“That ship sailed the moment Nicola Sturgeon stood side by side with the Tories last week,” said Ms Dugdale, referring to the Nat-Con alliance against Labour’s tax plan.

Mistaking word association for wit, the FM replied: “Just in the interests of accuracy, the ship of Labour campaigning hand in hand with the Tories hasn’t sailed, that ship, Labour ship, has been sunk - and has sunk Scottish Labour completely.”

As Labour MSPs complained about this distressingly mangled metaphor, PO Tricia Marwick slapped down a ruler and ordered them to “stop heckling the First Minister.”

Ms Sturgeon then turned to Labour's penny on income tax, claiming it would hit the low-paid.

“Liar!” called out Labour’s Neil Findlay from the back row, where the naughty kids sit.

Children’s minister Aileen Campbell pointed and tried to catch the PO’s eye like the class clype. “Oooh! He said liar, Miss. Miss! Miss! Over here, Miss!”

The PO said she’d review the official record to identify the source of the “unparliamentary language”, unless of course the dirty, wicked, hell-bound child responsible confessed.

“If the member who used that word wishes to admit it and withdraw it now, that will be very helpful,” she growled. “If not, I will take action this afternoon.”

There was a tense moment as Mr Findlay fidgeted close to tears, but he didn’t break.

The FM sighed. “We know how desperate the Labour Party is by the volume of the insults they sling across the chamber.”

She then called Labour’s plan “dishonest” and a “con trick”, which are wholesome parliamentary terms, and demanded to know how the iffy rebate bit would work.

“How much will it cost to administer? How will eligibility be assessed? How many of-”

Ms Marwick raised an admonishing talon and craned forward.

“First Minister, the Opposition puts the questions to you. You don’t put them to the Opposition.”

Ms Sturgeon’s face suggested no more apples for the PO for a while.

At the end of the day, Ms Marwick hushed the room and invited Mr Findlay to stand up.

Nervously hitching his short trousers, he said he would withdraw the unparliamentary term, and substitute the “dishonest” preferred by the FM. Ms Marwick fixed him with a hard stare.

“Mr Findlay, can I just say this to you. You have been a member of this parliament for almost five years. You know that the word liar, the word that you used at FMQs, is unparliamentary.

“I note what you have said and will consider the matter further.”

It could have been worse. He could have been a grown up with a real job.