About 14,500 students are expected to turn up in Arlington classrooms Tuesday, about 200 more than last year, most of them at the elementary school level.

School officials say they are exploring ways to ease crowding in the elementary schools. The school system has leased 13 portable classrooms that will be used at Glencarlyn, Barrett, Randolph and Abingdon elementary schools. This year, officials said, they will examine a major capital improvement program to deal with the long-term problem.

Kindergarten and first grade pupils at four Arlington elementary schools this fall will participate in an experimental computer program designed to help them learn to read and write.

The Language Arts Computer Pilot program will use Talking Text Writers that not only will display on a screen the words and letters a child types but also will repeat them out loud.

"We want children to see how reading and writing are connected," said Betty Ann Armstrong, supervisor of reading and language arts programs for the Arlington schools. "And we want to explore the possibility of how the Talking Text Writer can help children learn about language, how technology can enhance what we are already doing in both reading and writing."

If, for example, a child wants to type the word "get" but types only the letters gt, the computer will repeat just the names of the letters, Armstrong said.

The idea is that after several tries, the child would begin to understand that a vowel is needed to form a complete word, she said. Educators believe that the program also may be helpful in teaching the alphabet.

The Talking Text Writer, which was invented by Teresa Rosegrant, a professor at George Washington University, will be used at Taylor, Barcroft, Jamestown and Abingdon elementary schools. If successful, the Language Arts Computer Pilot Program could be expanded to other schools.

According to Steve Kurcis, director of instruction for Arlington County schools, the School Board appropriated $60,000 for the program as part of its mandate that school officials examine new ways to incorporate technology into classroom instruction and administration. "We're taking a long-range view, what the world is going to be like in 1990 and 2000, and technology is part of that world," he said.

Many successful pilot programs last year will be expanded this year, said Boyd Webb, associate superintendent. Among those programs is the Minority Achievement program, designed to improve academic performance of minority, particularly black, students. The School Board has increased the program's budget from $130,000 last year to $160,000 this year.

"We are starting to see increases in test scores," said Sharon Monde, who was hired recently to coordinate the program. Each school has submitted proposals of programs it hopes to institute during the school year, she said.

A pilot language immersion program, begun last year at Key Elementary School, will be expanded to include second graders in addition to first graders, Webb said. The program is designed to help children become fluent in a second language.

At the administrative level, five Arlington schools have new principals: Drew, Henry and Tuckahoe elementary schools and Yorktown and Wakefield high schools.

"It's unusual for us to have so many new principals," Webb said.

No changes are expected in the composition of the Arlington School Board.