At least five primary schools have scrapped the parent volunteer scheme which gives parents priority placement when registering their children for Primary 1.
The scheme is often seen as a way to get a foot in the door of popular schools.
But schools say they simply do not have enough volunteer opportunities for the flood of hopeful parents, many of whom will end up having to ballot anyway, despite having put in the hours.
Four of the schools are under the Singapore Hokkien Huay Kuan - Tao Nan, Ai Tong, Nan Chiau Primary and Kong Hwa.
St Anthony's Canossian Primary in Bedok North has also done away with the scheme.
While there are enough spots for every child to get a primary education, these are popular schools which tend to fill most of their places by phase 2B.
In this phase of the Primary 1 registration exercise, children of school volunteers who have clocked at least 40 hours of service are given priority to register. Children of active community leaders and those with church or clan associations also qualify under this phase.
The earlier phases - 1 and 2A - are for siblings of current and ex-pupils of the school, and children whose parents went there.
But it is getting more competitive for school volunteers, grassroots members and those with church and clan associations to secure a spot for their kids.
Last year, Tao Nan was oversubscribed by 61 per cent at phase 2B. It had 66 applicants vying for 41 places, and balloting was required for Singapore citizens living within 1km of the school.
In 2009, the school received 107 applications for 82 vacancies at phase 2B. The oversubscription rate was about 34.5 per cent and all Singapore citizens living within 1km got a place.
And the registration exercise looks set to get even more intense for the 40,000 six-year-olds enrolling this year in 187 schools.
Prime Minister Lee Hsien Loong, in his National Day Rally speech last year, said the Education Ministry will set aside 40 places in all schools for children who register in phase 2B and 2C. This is to make sure there would be places left in popular schools for children with no blood ties to them.
But the new rule also means there will be fewer places for parents registering their children in phase 1 and 2A. They might then have to face a ballot and might also join the volunteer queue to double their chances. This could make phase 2B more competitive.
So those who put in the volunteer hours might still have to go through a ballot, said Mr Adrian Peh, chairman of the Singapore Hokkien Huay Kuan's education committee.
"Many parents volunteered their time and effort but were not successful in securing a seat for their child. We understand their disappointment," said Mr Peh, who also supervises the management committee of the clan group's affiliated schools.
Mrs Cheong Ye Ling, principal of Kong Hwa School, said it already has a strong parent support group.
"Together with Singapore Hokkien Huay Kuan volunteers, the pool of volunteers the school can tap is more than enough.
"There is only so much work to do. If we purposely create work for parent volunteers for P1 registration, we are going against the original intention of giving parents an opportunity to experience the school culture," she said.
But the decision to do away with the scheme has caused disappointment for hopeful parents.
A father who declined to be named said he had bought a house within 1km of Tao Nan School. He had also intended to volunteer at the school to increase his chances of getting his child, now five years old, in. But that hope is now dashed, he said.