SEOUL -- South Korean high schools opened on Wednesday for the first time this year, with mask-wearing seniors returning to class in the vanguard of a phased plan to reopen all schools under strict protocols to prevent the spread of the novel coronavirus.

The beginning of the spring semester has been postponed several times since March as South Korea battled the first large coronavirus outbreak outside China, with classes held online.

But with daily coronavirus cases sharply down since a February peak, teachers with thermometers and hand sanitisers welcomed seniors in masks at their high schools on Wednesday.

“Schools have been anxiously waiting for all you students for the past three months,” Cho Hee-yeon, superintendent of Seoul Metropolitan Office of Education, told students at a high school entrance.

“From now on, we are entering an important phase where we need to succeed in both studies and [coronavirus] prevention.”

Some students put their arms around their friends’ shoulders but teachers told them to keep their distance.

Private sanitation contractors on motorcycles drove back and forth spraying disinfectant.

Under new health guidelines for schools, students and teachers must wear masks except at mealtimes, and are asked to wipe down their desks.

Windows will be open to improve air-flow, and desks spaced 1 meter (3 feet) apart.

Starting with high school seniors, schools will reopen in stages between May 20 and June 1 for all 5.5 million elementary, middle and high school students.

The education ministry keeps track of whether teachers or students have a fever using an online self-diagnostic system and anyone with a temperature over 37.5 degrees Celsius (99.5 degrees Fahrenheit) must stay home.

If any student tests positive for the virus, the entire school will switch to online classes until it is deemed safe for students to return.

Korea reported 32 new cases as of midnight Tuesday, taking the national tally to 11,110, with 263 deaths.