Immigrant children who arrive in the UK aged 12 or older are less likely to do well at school and to feel like they belong, according to a study.
It also suggests that the UK has a higher proportion of immigrant children than the EU on average.
The findings, in a new report by the Organisation for Economic Co-operation and Development (OECD), come amid a fresh Government push to encourage social integration in England's schools and communities.
The study, based on an analysis of the OECD's 2015 PISA tests which are taken by 15-year-olds across 35 nations and economies, shows that more than one in four students in the UK (28.55%) have an immigrant background, compared with an OECD average of 23.13%, and 21.49% across the EU nations that took part.
This proportion is similar to Germany (28.14%) and higher than EU countries including France (26.26%), the Netherlands (20.59%) and Greece (21.9%), but lower than in some others, including Ireland (33.72%) and Belgium (33.45%).
UK - 28.55%
OECD average - 23.13%
EU average - 21.49%
Compared with PISA tests taken in 2003, the percentage of immigrant students in the UK rose by nine percentage points, compared with an OECD average of around six percentage points and an EU average of around seven percentage points.
The study splits immigrant children into four categories: first generation - foreign-born children of foreign-born parents; second generation - UK-born children of foreign-born parents; native students of mixed heritage - those born in the UK, with one UK and one foreign-born parent; and returning foreign-born children - those born abroad to UK parents.
The findings show that in 2015, 73% of UK-born students of UK-born parents reached a "baseline level" of achievement in the 2015 PISA tests, which cover reading, maths and science, compared with 67% of all immigrant children.
But a country note on the UK also says: "In the United Kingdom, there is a considerably large penalty associated with late arrival of first-generation immigrant students."
It also says that while those who arrived in the country before the age of 12 were as likely as native students to achieve baseline levels of academic achievement, those who arrived when they were aged 12 or older were 27 percentage points less likely than native students to achieve this level.
Immigrant students with at least one UK-born parent had a similar chance of achieving baseline levels of achievement.
Baseline achievement means, for example, that in maths they can carry out basic arithmetic when instructions are given, and deal with simple maths problems such as comparing distances between two routes or converting between currencies, while in reading they can read simple and familiar texts, connect information and draw inferences and connect a text to their own experience and knowledge.
The OECD's report also says immigrant children who arrived in the UK at or after age 12 were 17 percentage points less likely than native students, and 20 percentage points less likely than immigrant children who arrived earlier in childhood, to say they felt a sense of belonging at school.
"The age at which foreign-born students immigrated is strongly related to the likelihood that they will report feeling a sense of belonging at school," the study says.
It adds: "In the United Kingdom, early arrivals exhibit no gap in sense of belonging compared to native students, while late arrivals are significantly disadvantaged."
Earlier this month, ministers announced a proposed Integrated Communities Strategy, which includes measures to boost English language skills and plans to require schools whose pupils come from a single ethnic or religious community to ensure they mix with children from other backgrounds.