In the Broadway classic "The Music Man," set in 1912, the con artist Harold Hill shows up in River City, Iowa, and attempts to persuade the otherwise contented townspeople that their youth are slipping into degradation. He singles out a billiard parlor, "the devil's playground," as the root.

"You got trouble," he sings. "With a capital 'T' and that rhymes with 'P' and that stands for pool!"

These days, you don't need goosed­up threats of nicotine stains and rebuckled knickerbockers to rouse the anxieties of parents. All you need is to broach the one subject that everyone views as Trouble.

By now, all parents know that technology poses at least some threat to children. Just last month, the American Academy of Pediatrics released a study that said while digital and social media can help early learning, they also come with a host of risks, including negative effects on sleep, attention and learning, along with higher incidence of obesity and depression. The group recommends that parents develop a Family Media Use Plan.

Fair enough, but what should be in such a plan? As the parent of adolescents, I want more than bromides. I want to know what other parents are actually doing that works.

For the last six weeks, I've circulated (on social media!) 20 questions covering topics like homework, passwords, bedtime and punishments. I received responses from more than 60 families, and though the survey was unscientific, the answers have already changed how we manage tech at my house.

FIRST PHONES

The vast majority of parents who responded gave their children their first phones in sixth or seventh grade, with a few holding out until high school. But those devices aren't always cutting edge. Parents opted for "dumb phones," "flip phones" or "hand­me­down phones" from siblings or grown­ups. They also turn off features, including Wi­Fi, Siri, even internet access.

Other popular restrictions include: "Writing an expected behavior contract." "No use of the internet on school days (except schoolwork)." "Screen time limited to 30 to 60 minutes per day during the week, unlimited on Saturday mornings."

Another is a partial ban on group texting. "I was able to help my son feel better about not having this by allowing him to view group texts on the family iPad," one parent said. "It helped him see how little value the group chatter has."

Phones during friend visits are another issue: "Nothing more disappointing than seeing my children's friends bring their devices to my home and have them focus on the devices to the exclusion of hanging out with my children."

My own favorite way to limit tech use: "Poor reception — the phones don't always work."

Asked to give other parents advice on when to give their children a phone, the consensus answer was: Wait as long as possible. Once you provide it, it's very difficult to take back.

HOMEWORK

Should children be allowed to communicate with friends while doing homework? Two­thirds of the parents say yes; one­third say no.

Among the comments by the Yeses were, "Only if they are in common areas of the house" or "Only with the door open (so we can monitor)." Another added, "Depends if they are working on a project together, which is difficult to enforce."

The Nos said that homework is done independently, and that if kids need help, they should find a parent, or the parents contact a teacher.

Wider use of computers for homework also drew mixed reactions. Some parents are quite strict, limiting all technology "outside of a computer for spelling or Google docs." "Only homework­related sites and no social media." "Only certain educational sites are allowed. Wikipedia is completely discouraged. I strongly believe that actual books should be read for research purposes as opposed to 'Googling' everything."

Others are more lax: "You have to let them use the tools they will need in their lifetime. Otherwise, let's give them coal and a slate slab, like Lincoln."

BEDTIME

Researchers at King's College London have found "strong and consistent association" between using devices at bedtime and inadequate sleep, poor sleep and increased sleepiness during daytime. Parents have gotten the message.

An overwhelming majority ban phones from bedrooms at bedtime. "Tech needs a bedtime, too, in our house, 30 mins before lights out." "No technology one hour before bedtime." "At 9 p.m. she brings her phone downstairs, where it stays until 7 a.m." "Devices are supposed to be parked outside the kids' bedrooms before they turn in for the night."

Some parents make exceptions on weekends or as kids get older. A few have no restrictions at all, though one otherwise tech­friendly mom said: "No earbuds! Our carbon monoxide detector went off one night and he did not wake up because he was sleeping with earbuds in."

At least one dad goes to the opposite extreme, turning off the Wi­Fi in the house at an appointed time each night. "Same rules, better enforcement," he said.

Also popular is to require phones to be charged outside the bedroom. "Everyone in our house puts phones on a charging station in our kitchen before going to bed." "Devices are charged in the kitchen. (I cook a lot and I can keep an eye on them, especially when the children are punished and still try to sneak off with them.)" "At bedtime, devices go in the bathroom for charging."

One mother has no specific place, only not in the child's room: "My husband and I simply ask where the phones are charging during our 'audits of responsibility.' If the children try to work around the rule, they know the device will be placed in 'jail.'"

SOCIAL MEDIA

Many parents restrict first­time phone users to a single social media platform. "Only Snapchat; no Instagram, Twitter, Facebook." "Only Instagram, and I check it occasionally." "One platform at a time."

Regardless of the sites, most parents insist on knowing passwords and logins. "My rules, until he was 18, were that I get all the passwords to all accounts. I did spot check from time to time." "I have ALL usernames and passwords, and if they change, she has to update my list. If I try to log on and cannot, I get the phone until it pleases me to give it back."

Do parents actually monitor their children's online behavior? Some do. "I read texts frequently." "We are 'friends' or 'following' all of his social media accounts, so we see every post." "I have asked to read texts when daughter was hiding device as I came into the room." "I do random audits. We talk about digital citizenship and positive words."

But others prefer to give their children freedom. "When they each began texting, I read random texts. And I asked about the ones I read. ('I see you and friend are chatting about the Jets,' or 'I see you and friend are chatting about another child in class.') That way they know I can read any text at any time, even though I don't." "They're almost all very boring."

PUNISHMENTS

What happens if children violate the family rules? Is it actually possible to separate a digital native from a device for an extended period of time? Behold, skeptical ones: Many parents say yes.

"Yes when younger." "Yes, she responds to it." "YES!! It's the ultimate motivator!" "Yes. Weeping and gnashing of teeth, and then they find other things to do." "I have. He gets very angry initially but eventually he calms down. Last spring I implemented a 3 week digital cleanse. He was angry each day for 3 days but also became more pleasant."

Another common way to get children to adhere to restrictions is to have them pay for overages. "We pay the fee but have her pay overages." "We also cut data off." "She now babysits family friends to earn more and has to learn basic budgeting."

FAMILY TIME

Perhaps the biggest complaint about technology is that it eats into family time. So what techniques have parents used to take back that time?

First, tech­free dining. "No devices for all meals." "No phones at the table, and that's not just at our house. Siblings, nieces, nephews and my mom's home have the same rule. No one gripes about it, they just do it." "No devices at meals. No earbuds in the car."

Second, consider positive alternatives. "Doing things that make phones a burden. Playing a fast­moving game, hiking, attending concerts or performances." "We watch movies together, have a fire in the yard or swim when it's warm and have game night, only board games allowed. They used to complain, but have found favorite games and look forward to it now."

"Do something constructive together. Make sure everyone (even mommy and daddy) get their hands dirty. We often will cook together and make some of the worst meals ever, but it's O.K. because we did it together."

Finally, when all else fails, many rely on the old parental standbys: threats, bribes and public humiliation. Threats: "Randomly I scream, 'Take that phone out of your hand!' It limits their use for the next five minutes."

Bribes: "Parent­child date night. (Parents alternate taking one child out for a treat; fourth week is parents night out.)"

Public humiliation: "If a device is picked up during family time, we get to open texts, and my husband and I do dramatic text reading."

Now that's a technique even the parents of River City might embrace. These days, trouble may start with the phone, but the solution still begins at home.
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Bruce Feiler is the author of "The Secrets of Happy Families" and the  forthcoming "The First Love Story."