This Is Instinct, Not Disobedience
Nipping at heels is the closing move of a herding sequence bred into collies, cattle dogs, corgis, shepherds and their mixes over generations: eye the movement, stalk it, chase it, and grip low to turn it. Your dog is not being spiteful when he darts at a running child's ankles — the behaviour fires automatically when something moves fast past him, and it feels deeply satisfying, which is why scolding afterwards changes so little.
Control the Trigger First
Until training is in place, your dog should not be loose in situations built from fast movement: children racing around a garden, football games, joggers streaming past in the park, cyclists on shared paths. Use a lead or a long line in those settings, position yourself between him and the action, and reward calm watching from a distance where he can look without launching. Every successful nip — even one that connects with a trouser leg mid-game — is a rehearsal that makes the habit stronger.
Build the Brakes: Leave It and Recall
Teach 'leave it' first on still objects, then on slow movement, then on the real triggers at a distance, paying generously every time he turns away from something he wants to chase. Practise recall the same graduated way, on a long line, so calling him off a moving target is a familiar, rewarded choice rather than a hope. Keep training sessions short and end them before frustration builds — a dog rehearsing self-control around movement is doing genuinely hard work.
Give the Drive a Legal Outlet
A herding brain denied any chase will invent its own, usually at the worst moment. Flirt-pole games, where he chases a lure on a rope under your control, let him stalk and grab on cue with rules and a clear stop. Large-ball herding games, scent work and structured tug all burn the same energy. Schedule these outlets rather than waiting for him to explode: a dog whose drive has been fed that day is markedly easier to keep mannerly around the children's games.
Children Need Their Own Briefing
Running, shrieking children are the strongest trigger most heel-nippers will ever meet, and children cannot be expected to manage a dog mid-game. Teach the children in his life to freeze and stand like a tree if he starts herding them — movement and squealing pour fuel on the chase — while an adult steps in and removes him calmly. If nipping is escalating, breaking skin, or aimed at visitors despite management, a qualified behaviour professional should assess him in person.
Watch His Body, Not Just His Feet
Herding arousal builds visibly before the first nip: the hard stare, the crouch, the freezing stillness, then the stalk. Learning to read those early frames gives you time to call him, scatter treats in the grass to break the sequence, or move him further away while he can still think. Handlers who intervene at the stare almost never have to deal with the nip; handlers who wait for contact are always one stride behind a dog moving at instinct's speed.
Because the plan only holds when every adult runs it identically, keeping his trigger list, his lead rules and his training stage in KinsLe under Care Teams means the person supervising Saturday's garden game works from the same page as you.