Parents hoping to get their children into three of the most popular primary schools might have to face balloting at what is considered an early point in the registration exercise.

As of yesterday, the schools which may need balloting at Phase 2A1 - the second of seven phases - are CHIJ St Nicholas Girls' (108 vying for 101 spots), Catholic High (121 for 118), and Henry Park Primary (110 for 101).

In the past, applicants at this stage would have got places but in recent years a handful of schools are facing a squeeze because of the rule introduced in 2014, requiring all primary schools to set aside 40 places for children in the later stages: Phases 2B and 2C. In 2015, children hoping to enter CHIJ St Nicholas Girls' had to ballot in Phase 2A1, which is for children whose parents are members of the alumni association or members of the school advisory or management committee.

Other schools which are more than 80 per cent filled are Ai Tong, Red Swastika and Nanyang Primary. A total of 43 schools had more than half of their spots taken as of yesterday, compared to 29 schools last year. In a bid to meet the larger number of Dragon Year babies - those born in 2012 - starting P1 next year, 2,600 more places will be made available, bringing the number to about 41,800 places.

Business owner Kam Sook Wei, 35, who registered her son in Anglo-Chinese School (Junior), said: "Based on history, the alumni phase is a walkthrough... although you never know what could happen because it is a 'dragon year'."

The next phase, 2A2, which opens next Wednesday to Thursday, is for children whose parents or siblings are former pupils, or whose parent is a staff member at the school. From this year, children from the kindergartens run by the Ministry of Education will also be able to apply during this phase to enter the primary school that shares a compound with their kindergarten.