And falling furthest behind are kids who have immigrated to Sweden during their primary education.
Among these, only 51 percent qualified for high school last year compared to 58 percent five years ago, according to the National Agency for Education (Skolverket).
The Swedish Schools Inspectorate (Skolinspektionen) is critical of the figures, charging that these students often don't get the education they deserve.
Moreover, not qualifying to receive a high school in Sweden will have a detrimental effects on the students' chances to compete in society and in the labour market, according to the inspectorate.
The inspectorate is especially of how schools treat students who have recently arrived in the country.
Often newly arrived immigrant children are all lumped together in a communal preparatory class, regardless of their different levels of education.
They can remain in such courses for several years, meaning they often they don't get a chance to study all the subjects on the standard Swedish schools curriculum, according to the inspectorate.
Sweden's deputy minister for education and minister for integration and gender equality, Nyamko Sabuni, thinks that schools must get better at mapping the education levels of recently arrived students and avoid placing them in preparatory classes.
“I strongly criticise preparatory classes where students are isolated with other new arrivals and separated from Swedish-speaking students. That slows down integration," Sabuni told news agency TT.
But she doesn't think that the problem lies in lack of financial resources.
“Most importantly, schools must be organised better. It is very much about following the guidelines that are there to ensure that these students have a better chance,” said Sabuni.