As a second grader, your DS can participate in JHU-CTY Talent Search by taking the SCAT, a super short multiple choice math and analogies test. Although not on the Davidson list of tests, a sufficiently high score would provide an objective supplement. Double check with your school administration because in early elementary, my kids were given ability/achievement tests for internal purposes, which scores were not reported to me, but which correlated/supported later test scores. There are also some "competition" type testing in math, such as MOEMS, Kangaroo, etc. If barring handwriting your DS is otherwise an exceptional writer, you can have him type or tape him telling you what to type.
