Sleep deprivation(缺失)is an important hidden factor in lowering the achievement of school pupils, according to researchers carrying out international education tests.

    It is a particular problem in richer countries with sleep experts linking it to the use of mobile phones and computers in bedroom late at night. Sleep deprivation is such a serious problem that lessons have to be dragged down to a lower level to suit sleep-deprived learners, the study found. The international comparison, carried out by Boston College, found the United States to have the highest number of sleep-deprived students, with 73% of 9- and 10-year-olds and 80% of 13- and 14-year-olds identified by their teachers as being negatively affected.

    In literacy(读写能力) tests there were 76% of 9- and 10-year-olds lacking sleep. This was much higher than the international average of 47% of primary pupils needing more sleep and 57% among the secondary age group.

    Other countries with the most sleep-deprived youngsters were New Zealand, Saudi Arabia, Australia, England, Ireland and France. High-performing Finland is also among the most lacking in sleep. Countries with the best records for getting enough sleep include Azerbaijan, Kazakhstan, Portugal, the Czech Republic, Japan and Malta.

    The analysis was part of the huge date-gathering process for global education rankings, the Trends in International Mathematics and Science Study(TIMSS)and Progress in International Reading Literacy Study(PIRLS)

    “I think we underestimate the impact of sleep. Our data show that across countries internationally, on average, children who have more sleep achieve higher in maths, science and reading. That is exactly what our data show,” says Chad Minnich of the TIMSS and PIRLS International Study Center.

    “It's the same link for children who are lacking basic nutrition,” says Mr Minnich, based at the Lynch School of Education, Boston College. “If you are unable to concentrate, to attend mentally, you are unable to achieve at your best level, because your mind and body are in need of something more basic. Sleep is a fundamental need for all children. If teachers report such large proportions of children suffering from lack of sleep, it's having a significant impact. But worse than that, teachers are having to adjust their instruction based on those children who are suffering from a lack of sleep. The children who are suffering from a lack of sleep are driving down instruction.”

    That means that even the children who are getting enough sleep are still suffering from this sleep-related lowering.

    Born on August 9,1963,New Jersey,Whitney Houston almost seemed bound to become a singer.Her mother Cissy Houston was the choir（唱诗班）minister at New Hope Baptist Church,and it was there that a young Whitney got her start.

    When she was 19,Whitney Houston was discovered in a nightclub by the famous Clive Davis of Arista Records. In 1983,Houston made her debut（首演）on national television.In 1985,she released her debut album Whitney Houston and almost immediately became a sensation.Over the next year,her hit singles Saving All My Love for You and How Will I Know helped the album reach the top of the charts,where it staved for fourteen weeks in a row. Houston won a Grammy in 1986 for Saving All My Love for You.

    By 1992,Whitney Houston was on top of the world,but her life was about to get very complicated very quickly. That year she married the R&B singer Bobby Brown.At first the marriage was passionate and loving,but things turned sour as the decade progressed and both Brown and Houston battled drug abuse.

    In spite of these growing personal troubles,Whitney Houston continued to progress in her career,crossing over successfully into acting in 1992 by starring in The Bodyguard.Her single from the movie,I will Always Love You, proved to be Houston's biggest hit ever,spending a record-breaking fourteen weeks on top of the US charts.

    In the late 1990s and early 2000s,Whitney Houston's increasingly rocky marriage,struggles with drug and health problems threatened her career.Over the next few years,Houston attempted to break her drug habit and divorced Bobby Brown in 2007.

    After almost a decade of struggling with her personal life,Houston seemed to be pulling herself together.She released a new album,I Look to You,in 2009.The recording received a warm welcome from music fans.

    In early 2012,Houston worked on a new musical film Sparkle with Jordin Spark.Unfortunately,Houston didn't live long enough to see it.

    Whitney Houston died on February 11,2012,in Los Angeles.With her passing,the music world has lost one of its most outstanding stars.

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    Pop music is the name for different forms of popular, commercial (商业) music. It had its beginning in the USA and spread throughout the whole world during the 1950s and 1960s. It is widely liked by the young people. The best known early form of pop music was “rock' n' roll”; another was “blues”. A more recent development is “folk-rock”.

    Pop music has taken the place of native music in many parts of the world; it has caused the number of people for jazz to become much smaller than it was in the 1950s and earlier, and it has now begun to rule musical stage productions. It's a big industry. Much pop music is without artistic value, but the work of some pop singers, e.g. the Beatles, Bob Dylan, the groups like Floyd and Crosby, Stills and Nash, is on a higher musical level. And there is still a great interest in it today. Pop music concerts and festivals take place all over the world.

    Ahead of the summer travel season, airlines in the United States usually compete to sell tickets and fill seats. But the airlines that operate the grounded Boeing 737 Max planes have a new problem: there are not enough seats to meet the demand.

    The revenue(收益)is right in front of them. They can see it, but they can't meet it, said Mike Trevino. He is an airline industry expert for Southwest Airlines Pilots Association, The grounding of Boeing's 737 Max came after two deadly crashes in five months. Southwest Airlines is the world's largest 737 Max operator. The company has 34 of the planes.

    American Airlines operates the second-most, with 24. These planes have been removed from use until at least August, The grounding of the planes has led Southwest to cancel 160 of its 4,200 daily flights between June 8 and August 5.

    American Airlines will cancel 115 daily flights, or 1.5 percent of its total summer flights .Southwest only flies Boeing 737s. It had estimated $ 150 million in lost revenue between February and March 31--mostly because of MAX cancellations.

    The 737Max was grounded worldwide in March following a deadly Ethiopian Airlines crash. It came five months after a Lion Air crash in Indonesia. All on board both planes died.

    Boeing is under pressure to provide additional software. Experts are examining the original software as a possible reason for the crashes.

    Boeing must prove to worldwide regulators that the plane is safe to fly. That process may take more than 90 days. Planes in the United States are usually mostly full during the months of June, July and August.