HONGKONG Chinese pupils in central London schools are outshining their English, Scottish and Welsh classmates to such an extent that politicians are calling for an investigation. For the second year running an analysis of the General Certificate of Secondary Education results at schools in the inner London borough of Islington shows ethnic Chinese students performed more than twice as well as pupils of English, Scottish and Welshorigin in last summer's exams. The analysis showed that about one-fifth of English, Scottish and Welsh pupils were not even entered for exams. ''This was a far higher proportion than for any other ethnic group,'' said councillor Mr Chris Webb, the Labour-controlled authority's director of education. Opposition Liberal Democrats said the results underlined the need for an investigation into the reasons for the different performances. Liberal Democrat councillor Mr Stephen Hitchins said: ''There is evidence to suggest that the superior performance of the Chinese and Asian pupils has a lot to do with their home background. ''But we shouldn't just shrug our shoulders and say there is nothing we can do. We need proper research into all the factors.''