Researchers from the University of Durham believe that there is a link between the use of fertility treatments, the trend towards women having children when they are older and the improving educational performance of twins.

Fertility treatments, which are responsible for an increase in the numbers of twins, tend to be used by more affluent and better-educated families - home backgrounds which make educational success more likely.

Researchers are engaged in long-term tracking of performance

In the past, twins on average have performed less well academically than children from single births - with researchers assuming that twins receive less undivided attention from their parents and less educational stimulation.

Long-term tracking

However, the Durham research - the Performance Indicators in Primary School project - which has used long-term tracking of pupils' performance, has found that twins are catching up with single-birth children.

The researchers also believe that older parents are better able to cope with the demands of twins - and the trend towards women having children later in life has helped towards reducing the performance gap between twins and single births.

Peter Tymms, director of the research project, says that the latest results show that "twins are now only very slightly behind the average - and it's nothing for parents to worry about".

Earlier research has shown that the gap between twins and non-twins is present when children begin school and persists through to later years.