It's the system or the teachers, you decide

An OECD (Economic Co-operation and Development) report is out stating that British kids have stagnated in standards achieved in core academic subjects by more than 500,000 pupils aged 15 in 65 countries.
Telegraph.

British schoolchildren are lagging dramatically behind their peers in the Far East despite a multi-billion pound rise in education spending under the last government, a major international study has found.
Standards achieved by pupils in the UK have failed to improve over six years as teenagers elsewhere in the developed world continue to pull ahead.
Figures published by the respected Organisation for Economic Co-operation and Development (OECD) compared standards achieved in core academic subjects by more than 500,000 pupils aged 15 in 65 countries.

I do wonder if the rise in education spending actually went on infrastructure rather than raising standards.
However I suspect the biggest problem our kids have isn't that they are less bright, but that the system is designed to hold them back and possibly too many subjects are taught along with occasional problems in schools where the first language is anything but English.
Years of meddling in the system by politicians trying to put right the degradations caused by leftard thinking have left us with a lowest common denominator system where the best are swamped by the mediocre. There's little or no streaming in schools, merely banding and the emphasis is upon passing an Ofsted test rather than actually teaching the kids something.
The teaching Unions themselves do not help matters by fighting like furies to keep incompetent teachers in place as well as their pilgrim system where activist teachers actually spend no time in the classroom and instead spend all their time on union duties (all paid for at taxpayers expense)
Our system was wrecked years ago when the comprehensive system was introduced, the retirement of the last able teachers from the era before has been the death knell for our kids when it comes to getting a state education. Envy and malice from the leftards reduced a system which produced a well educated generation into adult life into a mess which benefits no one and has employers bemoaning the fact that often enough kids come for interviews unable to read, write, do basic maths or even articulate a sentence verbally.
So I suspect we'll continue to slip down the league tables until we scrap the system we have and replace it with one that gets rid of political correctness, multiculturalism plus allows teachers to teach and keeps the unions out of education.
In other words, not for a long time.