The Prince George's County teacher's union is considering asking the county school system during the next contract negotiation to consider a new formula for calculating the student-teacher ratio for class size, a union spokesman said.

The new formula is "weighed" so children who are slow learners, handicapped or gifted will be counted as more than one student when the class size is computed, said Toby Rich, the president of the Prince George's Educator's Association.

Last week the teacher's union presented the new formula to the National Education Association in Minneapolis, Rich said.

According to Rich, the impact of the plan of the county school system in terms of additional teachers is uncertain until his staff works out the particulars of the new formula.

"We generally think of the class size problem as being one of sheer excessive numbers," said Rich.

"The truth is," said Rich, "the class size problem is not only how many are in one class but the kind of students."

Rich said the fast learner needs an enriched curriculum and challenge, while the slow learner requires special assistance in comprehending instructions and special material.

The teacher association president also said hyperactive children certified as emotionally disturbed should be considered as "two and one-half" students as well as those students who do not speak English.

Rich, who said pinpointing children with problems might be a problem in itself, indicated that the teacher's union was searching for a formula to assist teachers.

"Class size is a very fluid thing," said Rich, who added that some teachers have trouble handling a class of 30 students, if several of the students have special needs.

Rich said the new federal regulation for handicapped children, which will require the county to incorporate those children into the school system, will force this issue to come to light in the next year.

The whole concept of mainstreaming, according to Rich, implies that the handicapped child will "fit into the school system."