Parents hoping to enrol their children in three popular schools may have to face a ballot in the third phase of Primary 1 (P1) registration - Phase 2A2 - starting next Monday.

Nanyang Primary, Nan Hua Primary and Catholic High School are left with 10, eight and seven places, respectively, for Phase 2A2.

All three schools have also had more than 75 per cent of their overall vacancies filled.

Phase 2A2 is for children whose parents or siblings are former pupils, or whose parent is a member of the school staff.

The previous phase - Phase 2A1 - which closed on Tuesday, was for children whose parents are members of the school's alumni association or its advisory or management committee.

A rule introduced in 2014 requires all primary schools to set aside 40 places for children in the later phases of 2B and 2C, which is why there are limited vacancies in phases 2A1 and 2A2.

In last year's registration exercise, three schools that had more applicants than places for children in Phase 2A1 saw parents going through balloting for a place.

The schools were CHIJ St Nicholas Girls', Catholic High and Henry Park Primary.

Balloting at Phase 2A1 is considered early in the annual P1 registration exercise.

Last year, 40,600 children born in the Year of the Dragon in 2012 enrolled in school, necessitating 2,600 more places to be made available for the larger cohort.

The Ministry of Education has said that fewer children - 38,000 - are expected to register this year.