Herding is a sequence, and the park runs it for him
What owners call herding at the park is a working sequence firing in a playground: your dog spots movement, drops into the crouch and stare, circles wide to get behind the group and then chases to keep everyone bunched, sometimes finishing with a nip at a straggler's heels. Border collies and other herding breeds feel this most strongly, but plenty of mixed breeds run the same pattern. The other dogs are not livestock and many hate being managed; a chased dog who turns and snaps is answering rude behaviour, not starting a fight. Because the sequence rewards itself at every stage, your dog will practise it more skilfully every visit unless you interrupt the early links, long before the chase.
Win the recall before the crouch, not during the chase
Your recall has to land in the gap between noticing and committing. Call your dog the moment you see the head drop and the stare begin, while he can still hear you, and pay that recall like it is the best decision he ever made, with food he never gets at any other time. Practise that same recall on a long line in the park when no group is running, at easy distances, so the cue is already strong in that exact place. If he has already launched into a circuit, sprinting after him adds a second chaser to the scene; instead, move toward an exit line, call once when he arcs back toward you and reward the return, then put the lead on and reset the outing at a lower difficulty.
Redirect the drive into games where you hold the rules
A herding dog needs the chase-and-control game in his life, just under your management. Fetch played with a wait, a look at you and a release teaches him that self-control starts the fun rather than ending it. A flirt pole in an empty corner of the park or your garden gives him circling and chasing with a stop cue built in. Scent games, hiding treats or a favourite toy for him to hunt, tire the same brain through searching rather than pursuing. Book these outlets into ordinary days, not only park days, because a dog whose drive is regularly spent is far less desperate to spend it on the nearest running group.
Choose the park, the hour and the company honestly
While training is young, pick the quiet end of the park and the quiet hour, keep sessions shorter and leave after a success rather than staying until one rehearsal too many. Small, calm groups of dogs who know each other are a fair test; a chaotic crowd of sprinting strangers is not, and there is no shame in keeping the lead on near them. Watch the other dogs' faces as much as your own dog's: dogs who keep moving away, tucking tails or snapping over their shoulders are asking you to intervene. If heel-nipping has drawn blood or your dog cannot respond to any cue once aroused, a behaviour professional can build a graded plan in person. For planning each step up in difficulty, put a follow-up question to KinsLe's Kinny; he answers using the KinsLe Answers library.