Choosing a secondary school, Thomas and his friends know, is an important decision. Raising his eyebrows, one boy warns of the dire consequences of ending up in the wrong school. “Sometimes, they don’t teach properly, like,” he says. “Sometimes they do killings,” Thomas deadpans back. “I heard about it in the news.”

The 11-year-olds are among a handful of Birmingham pupils profiled in The Big School Lottery, a three-part documentary screened on BBC2. In part one, the vital, life-changing importance of choosing the right school is quickly established. We see one couple studying a map of their local catchment area: “So, as long as it’s a low birth rate, we might be in with a chance.”

This is Ethan’s hope. Or, more accurately, it is Ethan’s mother’s hope. Alison, first encountered during a mother-and-son yoga lesson, lives slightly too far from leafy Sutton Coldfield’s three high-performing comprehensives to guarantee her son a place. This is the cause of much smugness for her friend, Sally, who lives comfortably within walking distance of all three.

“I feel stressed enough now, and Phoebe’s more or less guaranteed to go to the school she wants,” Sally says. “I couldn’t bear to be under that pressure, and I think you do it amazingly well.” Alison looks ill at ease.

Over on the other side of the tracks, 28-year-old Simone is trying to avoid sending Jamiah to a school where he will be stabbed by gang members. Jamiah is keen on North Birmingham Academy, which used to be the second worst-performing school in the country. Simone prefers her own alma mater, the Catholic St Edmund Campion.

“Have you found out where the schools are in the league tables?” Simone’s mother asks. Simone, looking like she has been caught smoking behind the bushes, shakes her head. “Isn’t that your job?” she tries.

“But you’re always very quick to tell me Jamiah is yours,” her mother shoots back; it is a beautifully eloquent family snapshot.

The most sympathetic portrait, however, is of Saffiyah and her father. Saffiyah is applying for five local grammar schools; her father is helping her to prepare. “This is an easy day,” he tells her. “Last easy day, I had four tests,” Saffiyah returns.

The application is a team effort: Saffiyah’s mother is monitoring the family’s diet; her younger sister simulates the distractions of an exam hall. Her father, meanwhile, drives the route to the first exam in advance, to ensure against mishaps on the day.

By the end, genuine tension has been built: Ethan’s mother is threatening to move house if her son is not admitted to a decent comprehensive. Jamiah’s grandmother is planning to take possession of her grandson if neither the academy nor the Catholic school accepts him. And at least one viewer will be severely disappointed if Saffiyah fails to make it into grammar school. “Don’t forget to say ‘bismillah’ before you start the test, baby,” her father tells her. Then he kisses her on the head and leaves.

The next episode will be screened on Wednesday 15 September, BBC2, 9pm.