"I have a change of identity from day to day," she said. "If you don't have a secure view of yourself, you can be left asking, 'Who am I?' "

Monroe has been a substitute for five years, teaching English, science, math, art and other subjects. She said she enjoys the variety.

"Rather than having the same set of students for the entire year, I get to meet, literally, thousands of students from all different age groups in elementary, intermediate and high schools," she said. "I enjoy it, because I love the kids. I enjoy meeting people from all different backgrounds."

But substitute teaching provides no health benefits. Monroe has a bachelor's degree and would like to earn a teaching credential so she could become a permanent teacher. But for now, limited time and money don't allow that.

"I enjoy the variety, but as far as the future's concerned, it's year to year," she said. "All the prices are going up with the cost of living, and my pay is going down. It's all about survival."

Substitutes often don't know whether they'll work until they receive a phone call the night before they're needed. Some are hired on a long-term basis to cover for teachers who will be out for a known period. But substitutes don't receive any benefits unless they're hired for longer than 89 days to teach a specific class.

Some substitutes are retired teachers who want a supplementary income, while others are young and struggling to get by. School summer breaks can be long, dry periods with no paychecks. But many substitutes enjoy the job's flexibility, which allows them to pursue other interests and educational opportunities while gaining classroom experience.

Connie Wickware, another O'ahu substitute, is a licensed art teacher who hasn't been able to find permanent work in her field. She chooses to teach only at Radford High School these days, because there's a constant need for substitutes there and the school has made her feel welcome.

"There was a person in the main office who was very appreciative of me and of substitutes, and they went out of their way to accommodate substitutes to make them comfortable, and to make it work for them," she said.

It hasn't always been that way at some other schools, Wickware said. Little things, like not having a key to the teachers' restroom, can make a substitute's work tougher, she said.

"The bad thing about being a substitute if you go to a lot of different schools is the students don't know you, the staff doesn't know you, and you're not part of a school community," Wickware said.

But teaching many different classes at one school has benefits, she said.

"I see all the students in the school, and I love that," she said. "That's a good thing if you like the students, and I do."

Maui substitute Lorin Banks said a shortage of substitutes appears to be growing, and that it often seems like state officials just don't care.

"They just seem to feel like teachers and substitutes are recyclable," she said. "They'll get rid of us and they'll get new ones. They don't understand that the kids need to see the same teachers on their campus."