A boys school has blamed its drop to the bottom of the league tables on a shift in grade boundaries after it saw a fall in GCSE grades for the second year in a row.

Less than half of pupils at William Ellis School, in Highgate Road, Highgate, achieved the government’s target of five A* to C GCSE grades, including English and maths. The state secondary school saw an 11 per cent drop on last year’s results and a 27pc fall compared with its 2011 grades, figures released by the Department for Education (DfE) last Thursday showed.

Headteacher Sam White said William Ellis was “hit hard” by a shift in boundaries that saw a group of speaking and listening exams in English graded as Ds instead of Cs.

“It’s not an excuse, but we’re learning from it. We’ve lost the speaking and listening parts of the assessment, which don’t do us any favours, so we’re on track for this year,” Mr White said.

Mr White said 19 of 30 boys at William Ellis who took one of their English exams early this month achieved A* or As.

He hopes more will gain top marks later this year as this summer most will be sitting an English IGCSE, an internationally-used exam.

A national drop in GCSE results last year was blamed on a marking scandal which saw thousands of pupils miss out on a C grade in English after their exams were downgraded.

William Ellis and Regent High School, in Charrington Street, Somers Town, were the only ones to have less than half of pupils get five A* to C grades.

Schools in Camden, Barnet and Haringey exceeded the national average pass rate of 59.2pc, after falling just short of it last year.

Barnet was the best performing of the three boroughs with a pass rate of 71.5pc of pupils passing five GCSEs at A to C grade, including maths and English, followed by Haringey with 63.5pc and Camden with 60.4pc.

Once again, the area’s independent schools top the Ham&High league table, with the fee-paying all-boys University College School (UCS), in Frognal, Hampstead and Highgate School, in Haringey, coming top of the list.

UCS also ranked in the regional and national league tables, coming 10th-best in London and 75th in the UK.

All-girls Henrietta Barnett School, in Central Square, Hampstead Garden Surburb, was the area’s leading state school, with 98pc of teenagers getting five A* to C grades.

Camden School for Girls, in Sandall Road, Camden Town, overtook the all-girls La Sainte Union, in Highgate Road, Parliament Hill, to become Camden’s best performing state secondary.

Haverstock School, in Haverstock Hill, Chalk Farm, also saw a big improvement in its scores, which are up by 10pc compared with its 2012 GCSE results.

In west Haringey, Fortismere School, in Tetherdown, Muswell Hill, was the best state secondary school with 80pc of pupils getting five A* to C grades.

Students at Henrietta Barnett topped the A-level results tables just above independent all-girls South Hampstead High School, Maresfield Gardens, Belsize Park and Channing School, in The Bank, Highgate.

Hampstead School, Cricklewood, is now in the top 2pc of schools nationally for progress made in sixth-form studies over the last three years.

Pupils at fee-paying King Alfred School, in North End Road, Golders Green, had an average A-level point score of 807.9, ranking eighth for A-level results.

Its deputy head, academic Rod Jackson, said: “We always recommend parents regard league tables with caution and speak to us if they have any queries.

“Some of the data seems straightforward but, in the case of A-levels, the DfE figures are misleading and require much scrutiny to give a true representation of student performance.”