Some primary schools in Tuen Mun and Yuen Long are likely to almost double the number of first-year classes they offer for the next academic year with hundreds of extra places reserved for cross-border children, raising concerns over the schools' long-term sustainability. On a government list of 122 primary schools in seven districts that are expected to serve about 2,800 potential Primary One pupils living on the mainland, three - all from Yuen Long - have reserved 110 places each for the pupils, and 12 - from Yuen Long and Tuen Mun - had reserved more than 80 places each. The list, revealed yesterday, highlights the government's latest measure to ease pressure from cross-border children on North District, which had to turn away 1,400 potential Primary One pupils this school year due to a lack of places. Only 300 of the 3,000 places reserved for cross-border pupils are in North District. Tuen Mun and Yuen Long will provide up to 2,350 places and the rest will be offered in Tai Po, Tung Chung, Wong Tai Sin and Ma On Shan. Each of the three schools in Yuen Long on the list now has five first-year classes. Each school would have provided 10 places for cross-border pupils under a government requirement that every school on the list reserve at least two places in each Primary One class for such pupils. Assuming the three schools continue to assign 25 pupils per class, the extra 100 places would mean an additional four classes. Li Ka-to, vice-principal of Hong Kong Student Aid Society Primary School, one of the three Yuen Long schools, said that although the government would provide adequate resources for the classes, further problems could arise if the influx of children were to ease amid measures to stop mainland women giving birth in Hong Kong. He worried that the additional classes would then be terminated and teachers fired, affecting the healthy development of the school. "We can't reject pupils coming to our school at this phase," said Li. "They deserve our services. But there is a danger that some classes will be killed off in the future. This is not only our problem, but the whole education sector's."