你好，请看SSAT的Standby官方网站的相关解释：
Regular registration for the January 7 SSAT closed on December 16. Late registration closes on December 23, after which standby registration begins.

To select a test site for a national test date, click on the "Select a Test Site" button.
You may search test sites by location or location/test date.
Select a test date by clicking on a date below the name of the test center.
The date list will indicate whether a center is still available and whether late or standby fees apply.
When you click on the test date, your registration form will automatically fill in the test date, test center name, and test fees.
我也在帮一个学生报SSAT的STANDBY，不过点击进去日期显示是红色，无法再点击，你可以隔几天再看看。