B13

Sleep studies show that most teenagers don't get enough sleep and usually go to school feeling tired.

 USUAL

B14

The problem with the poor sleep is how you feel when you are not sleeping ­ sleepy, irritated or moody. Sleepiness makes it difficult to concentrate and to learn, and sleepy students often get bad marks.

 MOOD

B15

And it's not only about the process of getting education. Studies show that teens who don't get enough sleep have problems getting along with members of the family at home and their classmates at school.

 EDUCATE

B16

They are more likely to have family fights and bad headaches. Sleepy teens who drive cars may cause serious, even deadly accidents.

 DEAD

B17

Sleep scientists say that teens are programmed to go to sleep later and wake up later than other age groups. But many schools start classes early. Some American schools, for example, start classes at seven o'clock.

 SCIENCE

B18

Experts think that teens need more hormones for their normal growth and such types of hormones are made during sleep. What can schools do? Maybe schools should start classes later in the morning.

 GROW