Last Night's TV: Classroom Secrets/BBC1<br />Torchwood: Miracle Day/BBC1

Class 4FF, you are LIVE on BBC1, please do not swear!" Davina McCall's foghorn may have been absent but Big Brother loomed large over Classroom Secrets. The idea was to rig up a classroom at Humberstone Junior School in Leicester with fixed cameras, film the pupils and teachers for a week and then show the footage to staff and parents in order to root out the causes of "low-level disruption" and eradicate them together. A lesson in Big Society schooling, if you like.

The unsurprising revelation was that the causes of "low-level disruption" are children, so, short of an Orwellian purge, there's not an awful lot you can do about that. And while the parents and staff seemed to learn something from it, I wonder if anyone asked the children's permission to film them in those precious personality-forming hours away from the family home.

It was quite fun, in any case, to watch their impressive avoidance techniques. Alongside 21st-century tricks involving white boards and Cheryl Cole dance routines, the best distractions proved to be the timeless ones – sprawling and cheek-puffing, bubble-blowing, sharpener-stealing and urgent, whispered requests for tickles. Top marks went to Corey, who, floundering in literacy, pleaded hunger and was duly taken out of class for a piece of toast. After 20 minutes of his assiduous jam-spreading and crumb-clearing, the teaching assistant thought it time to chivvy him back: "You've missed half of class." "That's the whole idea," said Corey, licking his fingers thoughtfully. Clever boy.

There was a serious point to all of this, though. Chastened parents discovered that their little angels were in fact devilishly naughty or that they were struggling academically and socially far more than they let on at home. The school and its motivated young staff came across very well with their well-researched learning techniques and self-esteem booster sessions, if a little Supernanny-ish, in their interactions with parents. "If we could film children once a year and show it to their parents," said steely headteacher Annemarie Williams, "we probably would." The problem is that cameras, like an Ofsted inspection, can't really capture a school. The teachers are all on their best behaviour; the children, spawn of Big Brother, are on their scene-stealing worst. Take Maisie, a bright girl with a penchant for pulling faces. "I'm trying my best not to swear in front of the cameras," she whispered, Diary Room-style – a reality-show veteran, aged eight.

Otherwise, the programme turned up little. Schools will always have behaviour issues – looking to lay the blame at the door of parents or teachers is not all that useful. And spying on pupils is not all that healthy. "You've just got to leave a lot in the teachers' hands," surmised one parent. Well, yes. Schoolteachers shouldn't need fixed-camera footage for parents to trust them. I'm just glad that when I was eight I only had parents' evening once a year to worry about.

Emergency! Call Captain Jack! Somebody's stolen all the aliens from Torchwood! The racy Doctor Who spin-off for grown-ups has returned for a fourth series, this time with an injection of American cash. And so the first episode of this BBC/Starz co-production sees the CIA crash-landing in Cardiff, complete with helicopters, fireballs, a handful of well-known Americans (Bill Pullman, ER 's Mekhi Phifer, Six Feet Under's Lauren Ambrose) – and not a Weevil in sight. Even Jack didn't appear for 20 minutes, though when he did it was amid a hail of gunshots and suicide bombs. For a sci-fi agnostic like me this is no bad thing. The aliens are sure to emerge (from someone's stomach? A phone box? Oh, I don't know) in the next episode – but you can see why the purists might grumble.

For now, the really quite gripping premise of Miracle Day is that across the globe people have stopped dying. DOAs keep on living, death row prisoners can't be killed, even headless bomb victims continue to twitch on the slab. The implications for the planet are unimaginable – a population increasing by three million every two days while a paedophile and murderer who survived lethal injection is hailed as the Messiah. Meanwhile, Torchwood has been disbanded, Jack has disappeared and Gwen is living the quiet, if paranoid, life on a windswept Welsh farm with her new baby. Not for long, of course.

The story, unfolding over 10 episodes, is aimed squarely at the box-set market and while some may find the attempts to appeal to UK and US audiences alike a little trying, I rather enjoyed the fruits of this new special relationship. Russell T Davies's larky writing continues to shine and there are the same silly jokes but the trans-Atlantic locations are better and the special effects bigger (strafing helicopter vs open-top jeep on a Welsh beach? Why not?). As Captain Jack, John Barrowman is as plastic and unearthly as always, while Gwen – the most sympathetic of the gang – is now a dab hand at wielding a semi-automatic and a baby with the same arm. Of the new arrivals, Phifer as Rex Matheson is the one to watch, as his cool CIA persona comes under increasing pressure from the twin alien forces of the Welsh – "Wales is insane!" – and, well, aliens. Whether the story will sustain itself for another nine episodes remains to be seen. In the meantime, any apocalyptic American drama that makes jokes about the Severn Bridge at moments of high tension – "Wait a minute, I've got to pay for this bridge?" – has my vote.