Last Night's TV: Hold Me Tight, Let Me Go, BBC413 Kids and Wanting More, Channel 4

The Mulberry Bush school in Oxfordshire is a boarding school where children are sent when other institutions have given up hope of being able to contain them. It has 40 children and 108 staff, a ratio that seems generous until you see what the staff have to put up with. In the course of Kim Longinotto's marvellous film, members of staff at the Mulberry Bush were spat on, slapped, kicked, sworn at with a concentrated viciousness that would make a Scorsese film sound maidenly, and had their clothes soaked in urine. They bore all this with a patience that would seem saintly if it weren't dressed up in the modern secular jargon of reconciliation ("I want you to think about what you've done..."). And from time to time, they were rewarded with eruptions of spontaneous affection, need and longing: children flinging their arms around their teachers' necks, throwing themselves on their knees to propose marriage with mock fervour, howling at the prospect of leaving the school behind. The children slammed from one emotional extreme to another, and the viewer was left to trail limply in their wake, wondering how long anybody could keep up this pitch of feeling.

A neat summation of the film's moodiness came with the introduction of Charlie, aged around nine, who was warned that while he was at the school he would see lots of things that would make him think, "Goodness, what's going on?" Shortly afterwards, Charlie was seen standing on a desk, then waving a chair over his head while kicking out at a teacher. Goodness, you thought, what's going on? Here and elsewhere, the film seemed to show almost overwhelming surges of feeling, expressed with a boundless physicality, so that the teachers had to restrain the children in ways that, in other contexts, might be disturbing; but despite the strain visible on their faces, none of the teachers ever became overtly angry. As the title suggested, restraint and embrace can be hard to tell apart.

One of the great things about the film was its reluctance to offer simple diagnoses or to shrug blame on to the parents; though in the cases that were lingered over, a sense of having been abandoned, either physically or emotionally, seemed important. Calming down after an outburst, Ben told one of the staff that his mother had said she was "bored" with him. He hated himself, hated his life, he said, but then temporised – he didn't want to say why in front of the cameras. His interlocutor pushed him to go on – perhaps other children who felt the same would like to hear him talk. Ben said: "'Cos my mum stabbed my dad."

That exchange was important because it answered in part one of the anxieties such films inevitably raise: how far were the children acting up for the cameras? Here we were offered a reassurance that nobody was being fooled into pretending the cameras weren't there; and reassurance, too, that we weren't just being voyeurs. But the exchange mattered, as well, because of what followed, when Ben's mother came to visit on one of the six days a year that she is allowed to spend with him at the school. As she played with him in the garden, and then stroked his head as it lay in her lap, Ben for once at peace, the idea that she was nothing more than an uncaring or neglectful parent was happily scotched. What was going on here was far more complicated, far more touching than Ben's account made room for. Similarly, we saw another mother explaining to the school's family liaison officer how hard she found it to talk to her son on the phone, how guilty she felt when she saw him, and that saying goodbye didn't feel as bad as she knew it should. Every parent must have felt some shadow of those feelings: the sense that you can never be a good enough parent, never love your child enough.

This was not a doubt that afflicted the parents presented in 13 Kids and Wanting More. As Karan Johnstone explained, "I'm brilliant at being a mum. I'm probably the best mum I know." I envied her that level of self-assurance, while wondering whether more self-analysis might have been in order. On her 12th pregnancy, Karan was gloating over the prospect of once more having "that baby smell" around the house, the excitement of buying more baby clothes. You did wonder whether a Tiny Tears and a few tubs of talcum powder wouldn't give her the same thrill.

Then there was Mohammed, on number 11 and determined to keep going, despite his wife Noreen's visible weariness. Each pregnancy was God's will, he said, although a sceptic might point out that his proudly proclaimed aversion to wearing a condom was a factor, too. Mohammed is a local celebrity in Rochdale, not just because of the number of children, but because he is also unemployed and likes to attribute this, loudly and in public, to racism. He was quite an amusing fellow to watch, though the joke could, one suspects, wear very thin very quickly. This film didn't stop to examine what was going on in its subjects' heads in any depth; but the impression you were left with was of people who did not know when to say enough's enough. I'm like that with chocolate biscuits myself.

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