Wijit's permission means class sizes could exceed 50. But, even this measure will fail to accommodate all students yet to win a place at schools.

Eastern Bangkok is covered by Education Area 2, considered the most problematic in the country. There are 35 secondary schools and a total of 448 Mathayom 1 classes in the zone.

But about 10,000 of more than 30,000 secondary students have failed to win admission for the next academic year due to a lack of schools. The area is home to many school-age children because of rapid growth in housing and the opening of Suvarnabhumi Airport. Registration for places closes next Tuesday (April 10).

"Schools can now have more than 50 students in a class if they can accommodate that," Wijit said. "Every student must have a place to study."

But even with the class-size increase about 6,000 students are without a school, a ministry source said. Generally, class sizes are limited to 40 but schools have the authority to raise that to 50. Exceeding that requires Office of the Basic Education Commission approval. However, no school has asked for an increase yet, its secretary-general, Khunying Kasama Varavarn, said.

"Finally, we might ease the overflow by getting them into schools in neighbouring education areas and private schools," Kasama said. She wants Cabinet approval to employ more than 500 new teachers to met demand in Bangkok.

She noted that many schools were forced to rely on donations from parents to defray expenses not covered by the state per-pupil allocation. However, the government cracked down on donations after it discovered large sums were being paid by parents to get children positions at prestigious schools.

Her office needs an additional Bt105 million to build four new schools in area 2 and one in area 3, she said. But the minister said it was unlikely new schools would be finished before the start of the mid-May term.