Honestly, it is terrible. Gangs of teenagers head to toe in black often with their faces covered. I've seen them in town doing it (shouting at people, throwing food and drinks) and I work from home so am very rarely in town. I've also seen them on bikes in our (relatively 'nice') area. I drove DD home from sport one night around 10pm and they surrounded the car. I had to drive around the block and park elsewhere as they would have surrounded us again had we gotten out, it was pretty scary.
The online reporting form is a good idea, but the police do not act on any of these incidents with teenagers (even when a friends child was assaulted and injured by teens in school uniform caught on shop CCTV they said they wouldn't act).
Police are so under resourced that unless it is a domestic, murder, serious assault, serious drugs or sexual offences they just don't bother and with teens there are no consequences anymore so not worth wasting their time investigating.
With no consequences for teens committing all but the most serious crime and with no resources for youth clubs and services nothing is likely to change anytime soon unfortunately. I am sorry for your experience and will fill out the form the next time something happens.