When we first gave our daughters (then 13 and 15 years old) cell phones for emergencies, we made them sign an agreement in which we strictly ruled where and when they could use their phones and even we could check their every text message. However, in less than a year, we lost control of the situation.

There is a terrible reality that almost every teenager sends between 50 to 100 messages a day - some as many as 300, and 70% of teenagers admit hiding their online behavior from parents. According to a study, teenagers need as much sleep or more than they get as children - that's between 9 and 10 hours of sleep a night, but only 20% of them are getting it. When they don't get enough sleep, they perform poorly in school, feel very hungry, are more likely to have flu and are very emotional.

Recently, we adopted a "check in at tuck in" (盖被子时交手机) rule at our house, an idea I learnt from a parenting expert. It is very simple. At bedtime, when we "tuck in" our children for the night, they must "check in" their phones. They will probably bargain like this:

"But I use it for my alarm clock."

"I'll wake you up."

"My friends might need me."

"If there is an emergency, they can call the fixed phone and I'll wake you up."

A few weeks ago, when I drove my younger daughter to a friend's house for a sleepover, she handed me her phone. "I guess I should check this in now, since you won't be there to tuck me in tonight. I'll call you from Ellie's phone if I need you."

Passenger pigeons (旅鸽) were the most common birds in all of North America in the 1800s. It was common to see large groups of passenger pigeons — groups that made a sound like a storm. But today, they are extinct because of human behavior. Now, some scientists want to bring passenger pigeons back to life by using new technology and scientific ideas. They call this process de­extinction.

De­extinction has not happened yet. It is still just an idea. The process of de­extinction is not easy. First, scientists must collect DNA from the bodies of extinct animals. Then they will put it in the eggs of similar animal species. When these animals become adults, they will have babies. And these baby animals will have the DNA of the extinct animals.

Scientists believe it is possible to bring back passenger pigeons and many other animals. However, not everyone thinks this is a good idea.

Stuart Primm is the world's leading expert on modern animal extinction. He believes that bringing extinct animals back to life is bad for the earth. On one hand, these animals no longer have a safe place to live. On the other hand, they could cause other animals to die.

Many other scientists do not agree with Stuart Primm. Stuart Brand, a writer and scientist, is one of them. He believes de­extinction is good for many reasons.

"The current generation (当代) of children will experience the return of some unusual animals in their lifetime. It may be part of what defines their generation and their attitude to the natural world. They will take their parents to zoos to see the growing populations of passenger pigeons, and maybe even dodo birds. This will provide a good deal of money for zoos busy with extinct species restoration (恢复). Humans killed off a lot of species over the last 10,000 years. So, it's right to bring some back to life," he said.

Hard work really does pay off. Scientists find that perseverance (毅力) leads to better grades and higher achievements in school.

“Being passionate (热诚的) is not enough to ensure academic success,” said researchers, who thought of “courage” as a key to success. This is also regarded as effort in reaching long-term goals, and determination to continue one’s efforts in spite of hardships.

Researchers thought that the finding could help create new training to help children develop the skill and help ensure their future success.

Researchers from the Academy of Finland studied more than 2,000 students from Helsinki. They were followed through their academic career from 12 to 16, from the sixth grade until the ninth grade in local school years. Researchers found that the factor that best predicted courage was related to goals, with previous academic achievements playing no role in developing the skill.

Professor Katariina Salmela-Aro, who led the study, said, “Courage means a young person is really interested in his or her studies and does not give up easily. A key element of courage is high perseverance when facing difficulties and hardships. The important finding is that these factors are the key to success and well-being. Our study shows the power of courage.”

Professor Salmela-Aro also thought it was important to develop new practices and qualities to improve courage in teenagers. She added, “Young people should see everyday school work as part of their life in a broader context and establish achievable goals for themselves. Schools must also serve as a place where it is safe to fail and learn to deal with setbacks. One must not be discouraged by setbacks, but gain(得到) strength and new energy from them!”