a recent survey shows that the health of the students in our school has been going from bad to worse in the past three years. the number of short-sighted students has increased from 78.2% in 2002 to 92.5% this year,while that of overweight students from 36% to 52.4%. nearly 10% more students don't have enough sleep because of more homework. besides, over 15% more students become mentally unhea..