Hong Kong's educators on Thursday expressed concern over the secondary school students' participation in political assemblies, calling it a "worrying sign".

Hundreds of students, along with some teachers and parents, staged a rally at the Edinburgh Place, a public square in Central, adjacent to the Victoria Harbour, against the now-shelved extradition bill.

Some students said they would hold strikes every Monday starting Sept 2, the first day of the 2019-20 academic year.

Ho Hon-kuen, principal of Elegantia College, a local secondary school, called the assembly a "one-sided event" with no discussion on different views.

One of their demands was the release of all the lawbreakers arrested during protests, which is "very dangerous" and goes against the city's core value－the rule of law, Ho said.

Ho, who is also the chairman of a leading education group, Education Convergence, said that members of the secondary education system, including students, teachers and schools, should not be pulled into any political disputes.

Echoing Ho, Wong Kwan-yu, president of the Hong Kong Federation of Education Workers, said the secondary school students should not be involved in political activities, as they are not mature enough in handling and comprehending complex political issues.

Wong said their participation in the assembly on Thursday is a warning sign for the education sector and their parents.

These students could easily be incited, Wong said. Peaceful assemblies and strikes are usually the first step for anti-government protesters in inciting these immature students, he warned.

On Tuesday, Secretary for Education Kevin Yeung Yun-hung said the Education Bureau was against any form of strike. No one should use the school as a place to voice political demands or to use students to pressure the government, Yueng said.

Late on Wednesday, protests inside and outside the Yuen Long MTR station paralyzed traffic. At the same time, a relatively peaceful rally was staged inside the station.

Two men were arrested for unlawful assembly outside the station, the police said on Thursday. They were among about a thousand protesters who had gathered inside and outside the station on Wednesday.

They were protesting against the attack that took place at the station on July 21. They accused the police of failing to stop the attack.

At least 45 people were injured when a mob in white shirts stormed the station on July 21. A total of 28 people were arrested.

On Wednesday, the protesters blocked roads using garbage bins, signboards and barriers.

When the police baton-charged the protesters to disperse them, the protesters entered the station and confronted the police.

The MTR Corporation, the city's sole rail operator, expressed regret over the illegal acts of protesters at the station, and said it had lodged a complaint with the police.

A resident whose surname was Chen said the protesters stuck stickers on the rail card readers at the gates so the commuters won't be able to swipe their rail cards to exit the station.

Chen said he and other passengers left the station through a security exit.

Lilly Wang, another resident, said she took a bus to reach home after learning about the situation at the Yuen Long station. But the bus had to halt near the Long Ping Station, about 1.4 kilometers from the Yuen Long station, at the road ahead was blocked. She spent another 20 minutes walking home.

Rail services at the station resumed on Thursday morning, but the damage at the station was quite visible, according to Wang. Fire extinguishers were discharged by the protesters, and garbage bins were pushed over.