From County Tyrone in Northern Ireland comes word that Susan McGillan has earned an "A" on the GCSE exam, the General Certificate of Secondary Education for which students sit between the ages of 14 and 16 . "It was hard work," she told the BBC. But she added: "I found it absolutely rewarding. When you do the exam, you can value yourself." That's nice, you say, but so what? Well, first a bit of background: She came to her challenge from a slightly different direction than do most others. You see, at 84 , she is one of the oldest people on record to take the test. In 1936, when times were hard, she quit school to go to work in textile and then hosiery mills, rearing eight children along the way. She's now a great-grandmother five times over. Also physical problems limited her ability to attend the exam sessions, especially in the winter months. But because she isn't "much into television," she took up reading, especially about Irish mythology and the experiment with paganism 2,000 years ago. Then inspiration struck, and she decided to register for the tests. Flush with success, she plans to go back and tackle a higher level of examination next year.