This spring, SVT reported that the police in Rinkeby saw an increased trend of drug hiding in preschools in the Järva area.

In order to try to get rid of the youngsters who hang out in the preschools, a pilot project was started at the preschool Solbacken, which is on the border between Kista and Husby. Before the summer, an alarm was installed with a high-frequency sound, which, depending on the hearing, is perceived mainly by people up to the age of 25.

Inside the grille is the small speaker that will give off the annoying sound.

Social Security Council: "Cheap measure"

The results have been positive and the system will now be installed at four more preschools in Järva, which StockholmDirekt was the first to tell.

The measures are part of the City of Stockholm's security work. Each alarm costs about SEK 100,000 and is set aside from the city's security fund, which is a total of about SEK 100 million.

- Given the effect the alarm has had on this preschool, it is a very cheap measure to be able to create so much more security. Above all, it is an inexpensive measure in relation to what it costs for each Monday morning to have to come here and repair ruined things, says the Security Citizens Council Erik Slottner (KD).

There has been criticism of this kind of alarm in the past because the public can be disturbed, how do you do to avoid it?

- Preschools are not an environment in which to stay overnight, so I don't think that argument holds.

Isn't there a risk that crime will only be moved to other places?

- It is not true when we look at research but if it should be so - yes, then we must chase the criminals there. After all, we can't let a city stagnate and let places lapse with the argument that it will still just move to another place.

In the video at the top, the preschool principal explains how the situation has improved since the alarm was set up.