Children from households with same-sex parents are less likely to graduate from High School compared with children from opposite-sex married families according to a major new Canadian study.

The study is based on a huge 20pc sample of the 2006 Canadian census. This allowed a much larger than usual sample of gay and lesbian families to be studied.

The research found that, “Children living with gay and lesbian families in 2006 were about 65pc as likely to graduate compared with in opposite sex marriage families. Daughters of same-sex parents do considerably worse than sons”.

The study controls for the education levels of the families and still finds a difference.

It says it cannot yet be determined why children from gay and lesbian families graduate less often than children from opposite-sex marriage families.

Author Douglas Allen says that to determine this will “require an exceptional data set that not only identifies sexual orientation of parents, but also has a retrospective or panel design to completely control for marital history.”

The study, which is appears in the journal Review of the Economics of the Household, also critiques some of the existing studies in this area which claim that children from gay and lesbian families turn out no differently than children from opposite-sex households.

It says: “The samples used in these studies are often biased in some way, and the sample sizes are often very small. The one study that did use a large random sample and address a reliable performance measure (Rosenfeld 2010) turned out to draw the wrong conclusion, did not compare gay versus lesbian homes, did not examine the gender mix of the household, and did not control for parental marital status. As a result, there is little hard evidence to support the general popular consensus of ‘no difference’.”