As if waiting for the results of the SAT test did not provoke enough anxiety among high school students, those who register online to take the test now face a new source of tension.

Thirteen days after taking the test, they receive an e-mail message from the College Board telling them that their scores are available online. But to see them right away, the students must pay an extra $13. If they can wait another eight days, the message says, the scores will be available free, online and by mail.

Some longtime critics of standardized testing say the College Board practice reeks of exploitation.

''What is particularly cynical, and demonstrates the way they are using anxiety as a profit center, is that they can put the numbers up there, and then withhold what is already available,'' said Bob Schaeffer, the public education director of FairTest, a group in Cambridge, Mass., that advocates fair and open testing. ''I'm hard-pressed to think of another context in which people are so worried about their results, and there's price-rationing for data that are available without any extra work.''

The College Board said that the service was simply an extra option to lessen the waiting period for those who are anxious. The e-mail process, the organization said, is an expansion of a telephone service for early test results that has been offered for several years. The scores-by-phone charge is also $13 over the regular $25 cost of the SAT test.