Ismail Ajjawi, a Palestinian student denied entry to the United States last month at the airport in Boston, was allowed to enter the country on Monday and was at Harvard in time for the beginning of classes, according to Amideast, the group that sponsored him. Amideast said in a statement that the United States Embassy in Beirut had reviewed Mr. Ajjawi’s case and reissued a visa. Harvard officials confirmed that Mr. Ajjawi was on campus. Mr. Ajjawi, 17, landed at Logan International Airport in Boston on Aug. 23 and was turned back after immigration officials objected to his friends’ social...