When parents have unrealistic hopes for the academic achievements of their children, they may not perform well in school, says a new research.

"Our research revealed both positive and negative aspects of parents' aspiration for their children's academic performance. Although parental aspiration can help improve children's academic performance, excessive parental aspiration can be poisonous," Kou Murayama from University of Reading in England and the lead study author, said.

Researchers analysed data from 2002 to 2007 of 3,530 secondary school students and their parents from Germany.

The study assessed math achievement of the students as well as parental aspiration and expectation on an annual basis.

They found that high parental aspiration lead to increased academic achievement, but only when it did not overly exceed realistic expectation. When aspiration exceeded expectation, the children's achievement decreased proportionately.

The researchers attempted to replicate the main findings of the study using data from a two-year study of over 12,000 US students and their parents.

The results were similar to the German study and provided further evidence that parents' overly high aspirations are associated with worse academic performance by their kids.

The study was published in the Journal of Personality and Social Psychology.