Many Arlington public school children are in danger of being kept out of school this September if they cannot show proof that they have received immunizations against certain communicable diseases.

School officials are reminding parents that no student who has entered school since July 1, 1972, will be allowed to continue attending classes and no new students will be admitted unless parents can show proof that their children are immunized against polio, measles, rubella (German measles), tetanus, diphtheria and pertussis (whooping cough).

The law went into effect in 1972, and is being strictly carried out in public schools this fall for the first time. It also applies to private schools, but enforcement is carried out by individual schools.

Arlington School Superintendent Larry Cuban and school board members voted last May to strictly enforce the law after a measles epidemic last spring struck at least 125 children in Arlington public schools. "It was the measles epidemic that brought it to everybody's attention," said Dr. Marjorie Hughes, chief of school health services.

Most of the students who came down with measles last spring, however, had already been immunized against measles, according to Dr. Hughes, who said the students' shots were not effective because they had either received them before they were 15 months old, or were given shots containing a killed virus, or a live virus mixed with gamma globulin.

"I can expect that we'll have a bigger epidemic this school year," Dr. Hughes said, because that is the pattern of the disease, which traditionally appears in late winter or early spring. In Fairfax County, there were approximately 100 cases of measles during the 1975-76 school year, Dr. Hughes said, and during the past school year there were more than 300 cases.

Approximately 3,000 Arlington public school students do not have proof of immunizations, according to Dr. Hughes, and another thousand students probably have proof of immunizations, but received measles shots that were not permanently effective.

Parents of new students or those who entered school after July 1, 1972, must present an official immunizations, and the dates they were given, to their local school office. The record must be signed by a physician. Parents can bring the documents to school offices throughout the summer, and the schools are urging parents to do so before Aug. 15.

The only exception to the rule will be children whose parents submit a written request that the child be exempted from the state law on the basis of their religion, Dr. Hughes said.

Nearly 4,000 letters explaining the strict compliance regulation were sent home with report cards last June to parents whose children have entered school since 1972, Dr. Hughes said. If the proper immunization records aren't brought to the schools by Aug. 19, parents will be sent certified letters informing them that their child "will not be permitted to enter school" in September, she said. "They'll be permitted to enter school if they have started to get their shots," Dr. Hughes said, but "we'll keep an eye on them." Students who do not complete theri immunizations will be asked to leave school, she said.

Children can get immunizations from family doctors or from the Arlington COunty department of human resources. Immunization clinics are in operation at two locations this summer - the Edison Center, at 1800 N. Edison St., weekdays from 1 to 4 p.m., and the Fenwick Center, at 800 S. Walter Reed Dr., Thursdays from 9 to 11 a.m.

Two special late afternoon immunization clinics will be held July 26 and Aug. 30 at the Edison Center, from 4:30 to 6:30 p.m.

Medicaid recipients can receive the immunizations free of charge, and there is a nominal fee for other people. Children are required to have three doses of polio vaccine, one measles or combination measles/rubella shot, a series of three diphteria/tpertussis/tetanus shots or three diphteria/tetanus shots for children oveer 6 years old.