Rising numbers of secondary schools are struggling to keep up with demand amid intense competition for places, it has been suggested.
In some cases, families may now have to live less than a kilometre from a favoured school in order to win a coveted spot.
New analysis reveals that almost half of secondary schools in England are oversubscribed, and the numbers are increasing.
The findings come just days before 11-year-olds across the country learn what school they will be attending from September, on what is known as National Offer Day.
Figures obtained by the admissions website FindASchool, through Freedom of Information requests and data gathered from councils and schools, indicate that 47% of secondaries were oversubscribed in 2015 - equivalent to more than 1,500 schools - and this is up from 43% in 2014.
Primary schools in England have been struggling to keep up with demand in recent years due to a rising population, and this is now moving through into secondary schools.
The analysis, first reported by the Times Educational Supplement, shows that in some cases, so-called "catchment areas" - the area around a school from which it draws its pupils, may be shrinking.
A total of 28 schools had a catchment area of less than one kilometre in 2015, the website found. This is for pupils not qualifying for a place under any other admissions criteria. Of these, 17 were academies, five were council-run, four were foundation schools and two were free schools.
Admissions rules are set by councils and schools and they may prioritise other criteria besides using catchment area, such as taking the siblings of pupils already at the school.
FindASchool co-founder Ed Rushton said that the increase in oversubscribed schools was not a surprise given the growing school population.
"To date, the effects have been felt mainly in the primary sector, but the rising demand for places is now starting to affect secondary schools," he said.
Official figures show that 84.2% of children got their first choice of secondary school last year, down one percentage point from 85.2% in 2014.
And 96.4% got at least one of their preferred options, down 0.4 percentage points from 96.8% the year before.
There was a 2.3% increase in secondary school applications in 2015, the government data shows.
A Department for Education spokesman said: "The Government doubled the funding for school places to £5 billion in the last parliament, which has helped create half a million new school places. A further £7 billion has already been committed to create even more places over the next six years."