EVER have that nightmare where you are back in school, about to take an exam for which no studying has been done? That is child’s play compared to what happened to a group of primary schoolers from Bolton. These little angels came to assembly one morning to meet a new class, only to find it was made up of their mums and dads. Just for added chills, the oldies were wearing school uniforms. “Oh my God,” gasped one girl. “That’s. Your. Mum.” The horror, the horror.

The Class of Mum and Dad (Channel 4, Tuesday, 8pm) is the latest wizard but astute wheeze from the channel that brought you the award-winning “Educating” series and The Secret Life of Four-Year-Olds. The headmaster who came up with the idea admitted his peers might reckon he was bonkers. From the looks on the children’s faces, they weren’t too sure about Sir’s sanity either. But as he argued, it was a great way to show parents and guardians what goes on at an institution they were last in 30 years ago.

Lesson one was that their children were smarter than them, with one maths test reducing a mum to tears. The many rules came as a surprise, and the things the adults hated as children, such as PE, were still enough to bring on cold sweats.

On the whole, the children were a smart, switched on lot. To paraphrase the horrified girl at the start, “Oh. My. God. Could. It. Be. That. Schools. Today. Are. Not. Half. Bad?” Next week, in the second of six episodes, there is a run in with the headmaster for one mum. Good luck with that, Sir.

Sunny Point, the scene of the action in Agatha Christie’s Ordeal by Innocence (BBC1, Sunday, 9pm), continues to be a hive of misery, secrets and murder. Hooray! This week, it was Philip’s turn to be an absolute swine, and boy did he enjoy it. Sarah Phelps, who also adapted And Then There Were None and The Witness for the Prosecution, is pushing hard on the button marked “nuclear terror”, but I fancy the murderer of Rachel Argyll (Anna Chancellor) had more old-fashioned motives. My money is on Morven Christie’s housekeeper. Hidden depths there. Unless Christie is just unhappy that everyone else has wonderful costumes to wear and she’s in the sartorial equivalent of a dish rag.

There was more diving into the dressing up box in Secret Agent Selection: WW2 (BBC2, Monday, 9pm). The mission was to find out what it took to become a member of the Secret Operations Executive, Churchill’s hidden army of assassins and saboteurs who worked behind enemy lines. To that end, said narrator Dougie Henshall, a group of modern recruits would undergo the same tests as the wartime applicants. It was all going to be terribly authentic, serious, and educational. Hence the Allo, Allo costumes and hairstyles.

It was not, of course, exactly as it was. For a start, those clambering over ropes 60ft up had safety harnesses on. Far from every contestant being a potential recruit, some were clearly being set up to fail. The best bits were the mini biographies of the real agents, who genuinely did come from all walks of life, including the West End stage. Gay men, women, disabled people: if you made the grade back in those otherwise intolerant times, you were in.

I did like the way the training involved actors arriving out of nowhere to fire blanks every now and then, just to keep the trainees on their toes. Don’t try that in the day job, folks.

Farewell, then This Country (BBC1, Tuesday, 11.45pm), the mockumentary about a pair of clueless yokels that I dismissed as derivative and short on laughs. So you turned out to be funny, sweet, clever and nicely heartbreaking. So you cleared the decks at the Baftas. So everyone has been lining up to claim they always knew you were brilliant. I shall promptly send myself to TV reviewer detention, where they make you watch the first series of Only Fools and Horses then write out, 100 times, “I must not judge a comedy too soon. Or if I do I’ll only tell the dog.”

What a depressing old place Coronation Street (STV, Monday, 7.30pm/8.30pm) has been lately, problems piling up like cobbles, and a serial killer, Pat Phelan, on the loose.

Jenny Bradley (Sally Ann Matthews), of all people, made a bid to make things a little better down Weatherfield way. “I’ll organise a charity badminton match for racism,” she pledged.

“How about for anti-racism,” teased Mary’s daughter-in-law, Angie (Victoria Ekanoye).

Jenny took the correction in true Corrie fashion, waiting till Angie was out of earshot before sniffing, “She’s no Marti Caine, is she?” Ena Sharples would have been proud.