Sheriff's deputies began serving 78 Prince George's County teachers with subpoenas yesterday, summoning them to answer contempt charges for allegedly participating in a sickout that forced closing of three schools and created difficulties at several others.

The 78 were among 340 teachers who called in sick on Thursday, the third and last day of this week's sickout that followed the breakdown of contract negotiations with the school board; the 78 were the only ones who failed to produce notes from doctors when they returned to work yesterday.

The three-day sickout apparently ended yesterday, with all schools open and only the normal number of absent teachers.

The 78 teachers are being summoned to appear before Prince George's Circuit Judge William McCullough March 2 to demonstrate why they should not be held in contempt for allegedly ignoring an injunction the judge issued Wednesday night. If held in contempt, they could be fined up to $1,000 apiece and/or jailed for up to a year.

The subpoenas were obtained yesterday at the request of the school board. That prompted C. Steven Bittner, a teachers' union official, to complain that "the speed with which the board took this action is a form of harassment. This is a deliberate attempt to make the teachers look bad and embarass them."

The subpoenaed teachers will be defended in court by lawyers for the union, the Prince George's County Education Association, even though union officials say they didn't organize the sickout and didn't approve of it. "The union has a liability policy that gives us an obligation to come to the teachers' defense on any matter regarding employment," said Bittner.

At the union's office in Forestville yesterday, the phones rang constantly.

Most of the calls were from teachers asking whether they would have to get their own lawyers. Some were from teachers who said they did not know about the injunction and had legitimate reasons for calling in sick on Thursday.

Several doctors in the county said they saw slightly more teachers than usual in the last few days. "One teacher called and asked if I'd give her a note saying she had a cold," said a physician in Oxon Hill. "I told her no."

The job action followed the teachers' decision Monday to reject the school board's offer of a 5 percent salary increase in August, a 3.3 percent raise next February and an additional 1.1 percent raise the following April, a cumulative raise of 9.4 percent. Teachers argue that the offer actually amounts to a 6.8 percent increase over the course of a year.

The teachers have been seeking 20 percent raises and say they have lost 40 percent of their buying power over the last four years.