THE Union of Hongkong Secondary School Students will hold an extraordinary general meeting to vote on whether it should be dissolved. Student Gloria Lo Wing-yan, one of the founder members, said: ''The union will be disbanded if more than two-thirds of the members agree.'' The union, set up in December 1991, originally consisted of 15 executive committee members, 30 from the Representative Council, and about 150 general members. It has been on the verge of collapse since last December as positions in the administrative bodies - the Executive Committee and Representative Council - had not been filled. The sixth-former said union activities had been suspended after chairman Maria Chan Ka-yee, who was a South China Morning Post Student of the Year finalist in 1991, went abroad to further her studies last summer. Many problems were left unresolved following her departure and Ka-yee did not make any interim arrangements, said Wing-yan. Although the internal and external chairmen and several executive members had tried to take over the duties, she said they were unsuccessful because they failed to convene a meeting to discuss how to resume union work. New executive members were expected to fill the positions last December, but she said ''no one was willing to join''. Some students, who are now in Form 7, had to tackle the Advanced-level examination and some were engaged in university activities after gaining admission, she explained. ''At present, only a few members from the Representative Council who are now in Form 6 are willing to commit themselves,'' said Wing-yan, who is a former Representative Council member. ''I think we will leave the posts empty and suspend activities for a year,'' she said. ''Our main concern now is to prepare for an election of new executive members.'' They also hope to maintain close contact with members and at the same time recruit new ones. The union was officially set up by a group of secondary pupils to organise them into a group and to promote and strengthen communication among students. Other objectives are to promote student affairs in a democratic way and protect their rights.