A fourth-grade teacher at Patrick Henry Elementary School in Arlington called in sick this week, so Cintia Johnson agreed to help out. She escorted 12 students to a quiet corner of the school, where they sat in a circle and took turns reading aloud from "Indian Captive: The Story of Mary Jemison."

Johnson is not a substitute teacher. She is the school's principal. But in the scramble to find enough replacements for absent classroom instructors, even the boss is pitching in.

The struggle to find substitute teachers keeps getting worse, and Washington area school systems are weighing new proposals to ease the strain.

Some districts have proposed big raises in substitute teacher pay. Others are talking about new incentives to encourage regular teachers to take training classes after school instead of during school hours, which would reduce the need for substitutes. Administrators are advertising on school buses and trying to lure retired teachers back into the classroom.

Finding enough substitute teachers on a given day has long been a worry for school administrators. But the hunt has become more desperate as employment rates soar to new highs, reducing the pool of people interested in the work. Swelling student enrollments and new academic standards that require teachers to undergo retraining have exacerbated the shortage.

In fast-growing Loudoun County, as many as 200 substitutes are sometimes needed, but the school system usually has no more than 150 available. To increase the pool, school officials are proposing a 46 percent increase in substitutes' daily pay, from $65 to $95.

If the $600,000 request is approved by the School Board and the Board of Supervisors, it would transform Loudoun from one of the lowest-paying counties for substitutes to one of the highest. Other counties generally pay substitute teachers from $65 to $85 a day.

Loudoun administrators also want to establish a corps of 100 substitutes who will agree to work all 185 days of the school year. In return, they would receive health and retirement benefits and life insurance.

Howard County school officials are trying to lure former Howard teachers out of retirement by paying them $93 a day to be substitutes. In January, the district will extend that offer to all retired teachers in the Washington area. Other substitutes will get a $10 raise next month, to $75 a day for people with a college degree and $65 a day for all others.

Even with the promise of more money, substitutes don't like to be pinned down.

"We have subs who won't work on Wednesdays when Macy's is having a sale," said Suzy Zilber, a human resources administrator for Howard schools. "Or they'll say, 'No, it's too pretty--I'm playing golf.' "

In Fairfax County, administrators are proposing that regular teachers be paid $15 an hour next year if they attend training classes when school is not in session, an increase from the current rate of $10 an hour for after-school training. About 500 Fairfax teachers are absent each day because of training sessions on such topics as raising scores on the state's Standards of Learning tests, said Kevin North, the district's director of human resources.

In September, Montgomery County made a new offer to its retired teachers: If they returned to the classroom as substitutes for at least 60 days, their health care costs would be reduced to what they paid as active employees. The district also is considering a stipend for regular teachers who agree to attend training sessions outside of normal school hours.

Montgomery school officials have a list of about 2,000 people available to be substitutes, but only 500 of them can be counted on to fill in, said Elizabeth Arons, the district's director of human resources. On Mondays and Fridays, the demand for substitutes can rise to 700 or 800, leaving instructional assistants, guidance counselors and other instructors to fill in for the absentee teacher.

Prince George's County may be the only Washington area district that has managed to increase its pool of substitute teachers. In the last year, the pool has grown from 3,200 to 3,700, school officials said.

They attribute their success to a recruitment drive by principals, who are on the lookout for new substitutes among their school's volunteers. Application forms located at all 182 campuses make it easy for candidates to start the process of becoming a substitute, said Howard A. Burnett, the district's acting director of human resources.

Most area districts haven't been so fortunate. Arlington is advertising for substitutes on its cable channel, in newspapers and across the sides of school buses. It has appealed to its retired teachers for help and sought advice from the county teachers union.

"The substitute market is as tight as tight can be," said Arlington school spokeswoman Lisa Farbstein.