The Prince George's County Board of Education voted last night to allow students expelled under its tough policy on weapons and drug possession to apply for readmission to school.

The board also moved to reconsider the calendar for next school year after Jewish leaders criticized the removal of Rosh Hashanah as a holiday.

Under the current expulsion policy, adopted last September, dismissal is required on the first offense for weapons possession or second offense for possession of drugs or alcohol on school property.

Expulsions, if upheld by the board on appeal, were final. Some board members had criticized the severity of the policy when they saw that students with otherwise good behavior and academic records were being permanently removed from the system with no room for consideration of mitigating circumstances or background.

Three cases are pending in Circuit Court challenging the legality of the expulsion policy.

Under an amendment passed last night, expelled students may apply to the superintendent for readmission after being out the remainder of the term in which they are expelled plus an additional semester.

Application can be made no earlier than 45 days and no later than 15 days before the beginning of the new term. The amendment was made retroactive to last September and will apply to the 104 students who have been expelled this year.

Provision for readmission had never been necessary, board members said, because so few students were expelled; only one was expelled in the last year before the new discipline policy took effect.

"It's a harsh policy," said Angelo Castelli, its principal author. "It's severe and it was meant to be that way."

Castelli stressed that last night's amendment was not intended to weaken the board's stance against weapons and drugs. Chairman Susan Bieniasz said the board began to discuss providing for readmission to schools soon after it began hearing large numbers of expulsion appeals.

"Since the first of the year we have wanted to do it," she said.

The board also decided to reconsider another earlier action, the 1983-84 calendar approved March 10, after several representatives of the county's Jewish community complained of the lack of a school holiday for Rosh Hashanah. "The Prince George's County Board of Rabbis is shocked and amazed by the insensitivity of the Board of Education," Rabbi Gary Fink said.

The board had eliminated the Rosh Hashanah holiday, declaring that Yom Kippur should be the Jewish holy day observed in the autumn. This year, Rosh Hashanah falls on Sept. 8, a Friday, while Yom Kippur, Sept. 17, is on a Saturday when there is no school.

The board voted last night to meet with representatives of the Jewish Community Council of Greater Washington on April 11 before reviewing the calendar April 14.