If I send my SAT score report to my schools in November and tell it to send all my scores, will it also send the SAT subject test scores that I took in December?
Depends on which test registration you were in. If what you did in November was go into your December test registration and list colleges to receive scores, including having four free sends, and the Dec test was listed as one of the tests, then yes the Dec scores will be sent along with all prior scores. Just be aware that, in that case, your prior scores will not be sent until the Dec scores are released.
If instead you went into a prior registration and found prior tests and the Dec test was not even on the list or mentioned anywhere, and there were no free sends but instead you had to pay a fee per college, then all your prior scores have already been sent and that order is inapplicable to your Dec test and it will not be sent based on that order.
Thank you very much that helps.