The Director of Education yesterday decided to press ahead with a plan to add two more pupils to each primary class, despite the objections of more than half the SAR's teachers and principals. Helen Yu Lai Ching-ping called on educational groups to work for students' long-term interests, saying the increase to a 34.5 average class size was needed to speed whole-day schooling. But educational groups put out a statement last night reproaching the Government for ignoring their opinions and vowing to continue fighting the expansion in class size due to start with Primary One in September. About 20,000 of some 30,000 teachers and 800 of the 1,100 school principals have signed petitions objecting to the scheme. The statement said newly elected legislator Democrat Cheung Man-kwong would sponsor a motion debate and seek co-operation from other parties to urge the Government to shelve the plan. The statement said that by putting two more students in each class the teaching environment would be seriously damaged. But Mrs Yu said: 'This is a price worth paying for the benefits that whole-day schooling will bring to the learning environment of our children.' Mrs Yu said whole-day primary schooling would provide a better environment for students to learn and interact with peers and teachers. Deputy Secretary for Education and Manpower Joseph Lai Yee-tak said there was no plan to further increase the class size for the sake of achieving 100 per cent primary whole-day schooling. He said the timetable on this ultimate target would be announced in the coming policy address. To achieve the 60 per cent target by 2002, the department said it would build 72 more new schools over the next five years. It would also use all the 1,905 vacant classrooms where feasible. A total of 20,590 children - 67.5 per cent - in the Central Allocation of primary one places will be allocated schools of their first three choices on Saturday. Parents should obtain a registration forms at net area schools.