Prince George's County school officials obtained a court injunction last night prohibiting teachers from repeating their "sickout," which forced closing of two schools and disrupted many classes Tuesday and yesterday.

Teachers at a school board meeting last night said they expected to heed the injunction, but will persist in efforts to get higher raises in their new contract.

Board members decided at the meeting to increase their budget proposal to County Executive Lawrence J. Hogan by $16.4 mllion, to $310 million. But they refused to say whether the increase would be devoted to teachers' salaries or some other purpose.

As the board met, about 400 teachers packed its hearing room and another 500 waited outside in the rain. "I'm sick, sick, sick," chanted many of the teachers who were outside, while others carried placards proclaiming, "6.8 percent is too low," referring to the board's pay offer.

Teachers union president John Sisson called the board's decision to propose a higher budget a "guarded victory" for the teachers. "I think it opens the door," he said. Recent events have shown them that teachers are upset and concerned."

The sickout yesterday by approximately 400 teachers closed G. Gardner Shugart Junior High and disrupted classes in at least nine other schools. The work action, which was not endorsed by the county teachers union, involved more teachers than the one on Tuesday that closed Suitland High School when 71 of its 99 teachers called in sick.

Suitland reopened yesterday despite a shortage of teachers.

The injunction issued last night by Prince George's County Circuit Court Judge William McCullough quoted a provision of the teachers' contract prohibiting teachers from "participating in, calling, directing or abetting any strike, slowdown, or any action that interferes with the operation of the schools."

The injunction also quoted a contract provision prohibiting teachers from engaging in "an organized effort to take unwarranted sick leave."

School officials said the teachers' absentee rate was higher than normal throughout the county yesterday, but was particularly high at Suitland High, Shugart and eight other schools where principals had to recruit secretaries, supervisory personnel and substitutes to take the teachers' places. The result was that many students cut classes.

At Gwynn Park Junior High School in Clinton, students sat in the gym during the morning until school administrators could round up enough substitute teachers.

At Suitland High School, where numerous substitute teachers were working, many students spent their class time discussing the sickout, as well as more personal matters such as the appropriate gift to give a friend on Valentine's Day.

Jean Murphy and Teresa Douglas were among numerous students at Suitland who cut their afternoon courses after spending an unproductive morning in class. "There was no learning going on," said Murphy. "Why should I stay in school and do nothing when my soaps are on?"

Other schools hard hit by the sickout were: Overlook Elementary School in Hillcrest, Benjamin Stoddert Junior High School in Hillcrest Heights, Frederick Douglass Senior High School in Upper Marlboro, Fairmont Heights Senior High School and Hyattsville Junior High School.

At the 10 schools, 350 out of 520 teachers called in sick, according to school officials. In addition, approximately 50 teachers from other schools who called in sick were believed to be supporting the work action. There are 7,500 teachers in the county school system and 216 schools.

"We're talking about a small group of people," said school spokesman Brian Porter. "But one school is too many to be affected."

Even before the court action, union president Sisson, who denied prior knowledge of the work action, urged teachers to go back to work. "We greatly appreciate and understand teachers' frustration, but any contingent action of this type could prove counterproductive," Sisson said.

The teachers' work action followed their decision Monday to reject the school board's offer of a 5 percent salary increase next August, a 3.3 percent increase in February 1982 and an additional 1.1 percent the following April, a cumulative raise of 9.1 percent. Teachers say the proposed 9.1 percent figure includes the annual 2 to 3 percent step increase, so that the proposed annual cost-of-living increase amounts to only 6.8 percent -- far less than the 20 percent increase that they had requested.

"We lost 40 percent of our buying power during the past four years," said one teacher. "So asking for a 20 percent raise isn't all that outrageous."

Many of the 400 teachers who called in sick went to their doctors yesterday for eye exams and blood pressure checks to comply with a school board order that teachers get doctors' note or lose a day's pay, teachers said. Some teachers sent their lesson plans to school so substitute teachers would have something to work with.