@ckleslie The previous answer, above, applies in your situation. His being in high school til May 2021 makes him a full time student for 5 months. His being away for army training is only a temporary absence. As such, he is considered to have lived with you for more than half the year. Since he saved most of his income, he did not provide more than half his own support.
He qualifies as your dependent for 2021
