Plenty of parents figure young adults are so determined to drink alcohol after the prom or a graduation that it's best to take away the car keys and host a supervised party for their kids and their friends.
It's a long-standing tradition.
But starting Feb. 1, it's a finable offense for parents in Tempe.
The city is the first in the East Valley to try to curb underage drinking by making it easier to fine people who let these events happen.
The so-called social host ordinance is not a civil or criminal offense, which lowers the burden of proof for police to fine party hosts when they discover underage drinking at parties.
A first offense is $250. That can be reduced if the person takes a substance abuse class, said Bobbie Cassano. She coordinates the Tempe Coalition, which works to reduce underage drinking and drug use.
"We're trying to teach what the harm is, what the effects are, rather than saying you're a bad person," Cassano said. "The parents are doing what they think is a safe practice, but they may be harming other children."
Cassano points to research that the brain isn't fully developed until the ages of 21-25. Children who become regular alcohol users by 15 have a 40 percent chance of becoming alcoholics, compared with 7 percent who start at 21. Surveys of Tempe youth show the average age of first consumption is 12.5, which is earlier than the average in Arizona.
The fines are part of a larger effort to reduce underage drinking, said Kim Bauman, a Tempe social services manager who also staffs the Mayor's Youth Advisory Commission.
Work is underway on billboards, community presentations, teen-peer leadership and workshops on underage drinking.
Bauman said the campaign will work with parents who are uncomfortable with the issue or who don't know the latest research.
"A lot of people still see using alcohol underage as a rite of passage and they really don't have information about how using alcohol at a younger age can impact brain development," Bauman said.
Tempe's City Council passed the ordinance unanimously. It's part of an existing nuisance party regulation and its provisions include:
• A $250 fine for the first offense, a $1,000 for the second offense and $1,500 for each subsequent offense. The fines are meant to cover the costs of police breaking up unruly parties.
• The fines cover parties where alcohol or drugs are provided to people under 21.
• The fines can apply to a property owner, the person in charge of the site or a person who organized the gathering.
• Fines can be assessed to the parents or guardians of hosts who are younger than 18.
• Fines cannot be assessed to under-age people if their parents or guardians provide alcohol to them, as that is not illegal.
The ordinance is being watched by organizations in Chandler, Mesa and Phoenix, Cassano said.
The presence of Arizona State University plays some role in the problem in Tempe, but it's not a major factor, Cassano said.
"It makes it that much more accessible but we can't use that as an excuse," Cassano said. "We know it's happening in a lot of communities. It's not just Tempe."