Best friends forever? Well, maybe not - but schoolchildren who keep the same best mate as they move to secondary have been found to get better results.
A study of 593 found "substantial instability" in their friendships as they changed schools, with only 27% keeping the same best friend.
But the ones who did achieved better results and had fewer behaviour issues.
The researchers compared what they said about their friendships with how they performed in end of Year 7 assessments.
The University of Surrey study, published in the Journal of Educational Psychology, said: "During the transition, children may be more likely to lose best friends prematurely due to imposed school change rather than conflict or low-quality relationships, which may be the prevailing reasons under normal circumstances.
"Some commentators have suggested that the secondary transition may be a good opportunity to break ties with low-quality friendships because of the negative effects these can have.
"But little research has looked at the impact of keeping high quality friends."
Lead author Terry Ng-Knight, said: "We found that children who kept the same best friend over the transition tend to do better.
"Children's best friends change for all sorts of reasons but the transition is likely a big factor disrupting friendships.
"If we can find ways to support friendships during this time, this may help us to improve attainment and behaviour."
Most of those who had kept their best friend had gone to the same secondary school as them, according to the study.
Dr Knight added that secondary schools varied in the extent to which they actively supported pupil friendships.
Some schools asked children and parents to nominate friends they would like to remain with - but many others did not take friendship groups into consideration.