Filling teacher vacancies is a recurrent challenge for the public schools in the weeks before fall classes begin. However, the chronic teacher shortage, fueled by impending retirements of many baby-boomer employees of the state Department of Education, could easily reach acute levels unless strong leadership emerges on several fronts.

According to estimates reported this week, about 400 more teachers will be needed in classrooms statewide. Although officials believe this to be a manageable number, overall trends nationally as well as locally indicate that the state needs to ramp up its recruitment to head off a crisis.

The state is making advances in some areas, and that's good news. For example, special education is a hard-to-recruit field in which the teacher shortage has been whittled to an impressively low level.

Undoubtedly, various strategies have contributed to this success, and the state must examine ways to apply them to other specializations. Those in the recruitment field say special-education candidates have more flexible programs for earning teacher certification; surely this kind of flexibility would encourage potential teachers of other subjects to begin their training for the classroom.

One source of teachers that we're only beginning to tap is the military — or, more accurately, military personnel preparing for retirement and a second career. A nationwide incentive program called Troops to Teachers has in the past several years drawn 75 participants, some of them still earning their credentials and some already in the classroom. With the growing armed forces presence here, Hawai'i must promote the idea of a teaching career to military personnel, many of whom already have classroom experience.

There will be such an opportunity in mid-September when a Troops to Teachers consortium representing Western states will be here. Its members will speak at job fairs around the Islands and meet with education officials in search of ways to clear some obstacles to teacher certification. One proposal is to make teaching credits earned in other states more transferable; another concerns the need for teacher courses to be offered at times when those already in the workforce might enroll.

All these ideas and more must be explored if the state is to attract promising candidates to a profession so critical to our community.