Thousands of P7 pupils in Northern Ireland sat the first of this year's post-primary transfer tests on Saturday.
The AQE and Post-Primary Transfer Consortium (PPTC) tests take place on five successive weekends until 8 December.
The organisations say there has been a rise of about 8% in the number of entrants this year.
Some pupils will sit the AQE test in three further education campuses.
The annual tests are not run by the Department of Education (DE), but are used by the vast majority of grammar schools to admit pupils.
There are three AQE tests and one PPTC test on 17 November, although a supplementary PPTC test takes place on 8 December.
Primary school children aged 10 and 11 years can choose to sit either test, both tests, or decide not to take any of the tests.
According to figures provided by the two testing organisations, the number of entrants has risen again in 2018-19.
A total of 8,707 pupils have entered this year's AQE exam, up from 8,169 in 2017-18.
The PPTC said that about 7,800 pupils had applied to sit their GL Assessment test this year, compared to 7,150 last year.
About 2,000 children are expected to sit both tests.
Most pupils will sit the exams in grammar schools, but due to the large number of AQE entrants, about 600 children will take their tests in the Castlereagh and Titanic campuses of Belfast Metropolitan College and the Lisburn campus of the South Eastern Regional College.
The PPTC test, set by GL Assessment, is used mainly by Catholic grammars, while the AQE test is used mainly by other grammars.
Most grammar schools have been using one or both to select pupils since 2008, when the 11-plus exam run by the DE was abolished.
However, a consultation on the plan is yet to happen and there is no date set yet for a common test to be in place.