Dozens of children were convicted or cautioned for the first time in Caerphilly County Borough last year, figures reveal.
Long-term trends show far fewer children are being prosecuted now, compared with a decade ago.
The latest Ministry of Justice figures show 46 children were convicted or cautioned for the first time in the 12 months to September 2018.
The figure is a 34% drop on the previous year.
The data does not include repeat offenders.
Across England and Wales, the number of children entering the criminal justice has reduced dramatically over the last 10 years, by 85%.
In Caerphilly, the number being convicted or cautioned has dropped by 87%, from 367 offenders in 2008.
Just for Kids Law, a charity which helps ensure children’s legal rights are respected, said that despite the decrease, it still has concerns around youngsters entering the criminal justice system.
Chief executive Enver Solomon said: “These figures show the benefits to society which come when police and youth offending teams focus on diverting children from the criminal justice system, rather than punitive methods that do little other than funnel them into a life of crime.
“We are concerned, however, that progress could be jeopardised by knee jerk policies such as the new knife crime prevention orders, which are likely to drag a large number of children into the criminal justice system.”
Mr Solomon said there were still “many outstanding issues”, such as holding children in police cells for extended periods of time and poor quality legal representation.
“Children have different needs and entitlements to adults, but too few lawyers are specialists in how to work with them, leading to missed opportunities to divert young people from the justice system,” he added.
The figures also show that Caerphilly has a higher rate of youth offenders than Wales does on average.
There are 278 children cautioned or convicted per 100,000 youngsters in the area, compared with 209 per 100,000 across the country.
The child criminal capital of Wales is Newport, with 375 youth offenders per 100,000.