About a dozen Prince George's County educators took their plea for higher salaries to the Board of Education last night, pressing officials for movement in 7-week-old contract negotiations.

"I came tonight to tell the Board of Education why I will be forced to leave the teaching profession," said Suitland High School science teacher Elizabeth Heibert, her voice quivering as she spoke.

Heibert, who said she wanted to take a second job but must spend her nights correcting papers, said, "It's very difficult to make ends meet." She ended her testimony abruptly when she broke into tears.

Teachers and administrators, who made up about half of the speakers at a 90-minute hearing scheduled to discuss Superintendent John A. Murphy's proposed fiscal 1987 budget, argued that their pay is far behind that of other school systems. The county has the lowest starting pay in the Washington area, at $15,738 a year.

Murphy's $381 million budget, proposed Jan. 8, calls for a 6.5 percent increase over this year's budget but does not yet include funds for pay raises for teachers. The board must act on the budget by March 1, when it goes to the County Council for further action.

Teachers are in the second year of a two-year contract. Their union has accused the board of stalling in the negotiations and confusing issues by offering a complex set of raises to be phased in over two years.

School officials say the typical teacher would, under their proposal, receive a raise of about 17 percent over two years. But Paul Pinsky, president of the Prince George's County Educators Association, said that when already budgeted step increases and delayed raises are taken into account, the proposal amounts to an increase of only 2 percent to 5 percent.

The association representing school administrators argued that supervisory staff also need raises and that class size should be reduced. Prince George's has the largest average class size in Maryland.

Madeleine Errickson, of the Home and Hospital Teachers Association, asked that such teachers be paid for planning time and given some benefits. She said some teachers have worked in homes or hospitals for 20 years without benefits.