Adults that hate kids tend to do dangerous overtakings because they just can't chill for a bit at 30 km/h and so on. It's not the kids and their tractors making the roads more dangerous.

Disregarding just being teenagers (using their phones, doing burnouts), not having a proper driver's license (usually a 20+ lesson affair in Sweden) and driving old cars without safety systems; driving at less than half the speed of regular traffic in a smaller city or a more rural area means a lot of dangerous overtaking as the standard road is one lane in each direction (especially where the terrain doesn't allow for much more) and these cars are not allowed on highways. Since you are allowed to choose high school in Sweden, some choose one further away and driving. Making such roads congested.

They tend to lead to more unsafe overtakings since getting stuck behind one is stressful, they’re driven by young people who have a license to drive a moped and haven’t gone through the ice-driving classes a regular Swedish driver’s license includes, and the cars are often older inherently unsafer car models lacking proper maintenance.

And a chunk of people driving them violate the framework and drive extra passengers, bypass the speed limiter, and drink and drive.