PHNOM PENH -- Secondary school students in Cambodia's capital Phnom Penh returned to classrooms on Wednesday, marking a milestone in the Southeast Asian nation's battle with COVID-19.

For the first time since February, many of the almost 140,000 pupils in the city sat for in-person lessons at both public and private schools that had been certified as safe by the Ministry for Education.

All teachers and school staff were required to take rapid COVID-19 tests prior to returning to campuses. Twenty-four out of more than 10,000 tested positive, according to local media. Students and staff were also made to show vaccination cards before entering school grounds, where masks are mandatory.

Elsewhere around the country, schools continued to welcome back students in areas with low infection rates.

Grade 10 student Neang Bein, who attends high school in the eastern province of Svay Rieng, said she was eager to get back to normal. Months of online learning had led to headaches and back pain, she complained.

"I can't wait to walk into the school, meet my teacher and my friends," she told Nikkei Asia on Tuesday. "I can't remember the last time I was there."

Since the pandemic began, schools in Cambodia have been shut for more than 200 days, facing even tougher restrictions than restaurants, bars and many businesses. The prolonged closures have deepened existing inequalities in Cambodia's under-resourced education system, highlighting a digital divide between students with the resources to study online and pupils without such means, according to UNICEF.

Cambodian Prime Minister Hun Sen in late August pushed for rural schools to resume classes, noting children in the countryside who struggled to access digital learning were at risk.

"We need to act wisely, flexibly, and manage the situation well so that we can accelerate the nation's development, especially the promotion of human resource training," he said.

"Otherwise, our children will drop out of school and even forget the alphabet when they are not learning."

The school reopenings are the latest positive development for Cambodia.

Although still facing rising case numbers, with total infections surpassing 100,000 and deaths hitting 2,000, the country has outperformed its wealthier neighbors and even many developed countries in vaccinating its citizens.

The government has set targets of inoculating 10 million adults and 2 million children aged 12 to 18. As of last weekend, more than 8.5 million adults had been doubled dosed and another 1.1 million were awaiting a second jab.

In the 12 to 18 age group, more than 1.7 million have had at least one jab, with over half of that number having received two shots.

The country received some AstraZeneca stocks via the United Nations-backed COVAX program and the U.S. has donated more than 1 million doses of Johnson & Johnson. However, the bulk of Cambodia's vaccines -- more than 26.8 million doses -- have come from China.

Last weekend, China's Foreign Minister Wang Yi pledged a further 3 million doses during a visit to Phnom Penh. He also promised $270 million in aid and inaugurated a new stadium built with a $150 million grant from China.

The additional stocks will bolster Cambodia's booster shot campaign, which has so far delivered a third dose to more than 780,000 people including Hun Sen, who received an extra jab on Tuesday with his wife.