The mental capacity of adolescents may improve or reject a much larger scale than previously thought, according to a new study.
So far we have assumed that the intellectual capacity, as measured by IQ remains fairly static throughout life.
However, tests for adolescents at a mean age of 14 years and then repeated when the average age was about 18 improvements found - and deterioration.
The findings are published in the journal Nature.
That have implications for how students are evaluated, and the age at which decisions are made about their future.
The study included 19 boys and 14 girls who underwent a combination of brain scans and tests of verbal and nonverbal intelligence in 2004 and then in 2008.
The results show that a change in verbal IQ was found in 39% of adolescents, with 21% showing a change in the "performance IQ" - a test of spatial reasoning.
The results are considered to have greater validity, because for the first time, variations in IQ related to changes in two particular areas of the brain of adolescents.
An increase in verbal IQ corresponds with an increase in the density of a portion of the left motor cortex - an active region during speech.
And an increase in non-verbal IQ correlates with increased density anterior cerebellum - an area associated with hand movements.
The work was led by Professor Cathy Price Wellcome Trust Centre for Neuroimaging at University College London and published in the journal Nature.
The paper suggests that the results would be "encouraging for those whose intellectual potential can improve ... and a warning that students can not maintain their early potential."
Professor Price said: "We tend to evaluate children and determine the course of their education relatively early in life.
"But here we have shown that their intelligence is likely to be developing.
"We must be careful not to write more poor artists at an early age, when in fact their IQ can improve significantly given a few more years."
The research does not seek to understand the causes of the changes.
One explanation is that teenagers mature at different relative ages - with "principles" and "late" developers - while the rules relating to education can play a role.
One participant, Friston Sebastian, now 23, showed a marked increase in IQ between the two tests - half to one of the highest categories.
Educated in the public sector, he said he had struggled in their early years, in need of repair math, but is now planning a doctorate in computer engineering.
"I think the change was in school I started doing things that really interest me, which was dedicated to, then I found it easier and more interesting."
The research was funded by the Wellcome Trust, one of the many projects supported within the program of understanding the brain.
Future work may focus on how to adapt the brain may be beyond adolescence, and the implications for the fight against mental illness and other neurological diseases.