单选题 Competition makes losers as well as winners.This fact makes a simple rule for judging when it is useful to society and when it is dangerous.Can we afford to look after the losers?They are not going to vanish. Education is a typical example.The market，and the self-interest of parents，would ensure that good schools flourished and bad ones—well，they would disappear.Yet authorities still must ensure that every child has a school place in order to avoid discontent among parents even while the means to do so has largely vanished now that two thirds of secondary schools in Britain are academies which they do not control.

By encouraging parental choice in schools，successive governments hoped to harness the ambition of families to give their children the best education possible.But this ambition is by its nature limited.It does not extend to Other people's children.In fact，"it is not enough to succeed;others must fail".The burden of student loans increases the price of failure for those who fail to get into the "right" universities or study the "right" subjects.The result is an increase of inequality without any corresponding increase in quality at the top.

One measure of this is house prices.State schools with a good reputation increase the price of houses in their catchment areas (学生来源地区) substantially.A survey showed that outside London parents were willing to pay up to three times the average price for a house to get their children into desirable schools.Catchment areas operate as a kind of pre-exclusion mechanism，which keeps poorer children out of good schools.In all this，both schools and parents are responding to the competition as a zero-sum game.We are all poorer as a result.

It is arguable that the cost of bad schools to society，as well as to the children involved，far outweighs the benefits that competition has brought the good ones.School systems should be judged on the basis of their worst performances，not their best.

What's the purpose of successive governments in education competition?无