England's performance in the latest Pisa is "encouraging", the official behind the tests says in message to this country's teachers.
But Andreas Schleicher, who runs the Programme for International Student Assessment for the OECD, cautions that more needs to be done to inspire pupils in English schools.
In the latest results of the Organisation for Economic Cooperation and Development's tests, sat by 600,000 teenagers across 79 countries last year, England's scores in maths improved significantly, while there was a smaller boost seen in reading scores.
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Mr Schleicher said the results were "positive" but that there was still work to be done before England can rival world-class education systems such those found in Finland, Estonia or the Chinese provinces that take part in Pisa.
"We have seen some encouraging developments, particularly in the field of mathematics, where you could see learning outcomes clearly on an improvement path, which should be credited to what is happening in the classroom and the work of teachers," Mr Schleicher said.
In maths, England's score improved by 11 points since the last Pisa tests in 2015, achieving an average score of 504, which puts it in 17th place in the rankings.
However, it is still behind high-ranking systems in Finland and East Asia.
In reading, England improved by five points with an average score of 505, but in science, England's average performance fell by five points since 2015 to 507 this year.
Mr Schleicher added: "In other subject areas the direction of travel seems to be positive – England is no longer a country where social disparities are unusually wide – they exist, and social background is still quite an impactful drive on learning outcomes - but you can see education systems increasingly being capable to moderate social inequality."
The latest data shows that the attainment gap between the least and most privileged in England is similar to the rest of the OECD, but the proportion of pupils who succeed academically despite their socioeconomic background was larger in England than it was in other OECD countries on average.
"We have an isolation index in Pisa – to what extent do children from disadvantaged backgrounds get a chance to go to a school with excellent performance standards, and you can see that that is no longer one of the biggest barriers, so I think there are many promising signs," said Mr Schleicher.
"Obviously, there’s a long way to go to reach the world class education systems like Estonia in the OECD area, or in east Asia.
"There’s still a significant gap both on quality and equity but I do think England’s teachers should be proud of this."
However, Mr Schleicher said England's teachers needed to do more to inspire their pupils, adding that a lack of collaboration between teachers in England could be hindering this.
"When you look at work organisation, teacher enthusiasm as experienced by students is in the middle place – teachers could probably do more to inspire learning, and that of course commands a significant degree of professional autonomy, and a collaborative culture.
"Teaching is still quite atomistic in England – teachers teaching in isolation in the classroom, and having less time for things other than teaching."
He said teachers should be given time to work with colleagues or explore pedagogical research together, as could be seen in in the Chinese provinces, which have the highest-ranking education systems in Pisa.
He added that working with other teachers to "to design innovative plans for students" would also benefit England's school system, "which is where the Nordic countries, Estonia and Finland are very strong".
"So, these are areas where I could see room for further growth, but for the moment, I think teachers should be proud of where things stand," Mr Schleicher said.