so most top schools require to see all tests taken but if I send in my ACT plus subject tests will my subject test report include my ancient and generally awful SAT score?
I believe not. If you send ACT and JUST the practice tests, then they wouldn’t send the SAT. They make a profit from making us send scores XD, sending the SAT scores for free, and without your permission, would not be advantageous for them.
If you are sending the SAT scores, there is a way to selectively suppress what you don’t want sent.
However, it is a good idea to meet the rules as required by individual schools, i.e., if they want all scores, you are expected to send all and you are breaking the rule if you don’t do so. If you have an ancient SAT score and you have not retaken it, it is not a bad thing to let them see it if they require you to do so. That is not the same thing as sending it to everyone even if they don’t require.
Sending your ACT is done through ACT.org, which has nothing to do with SAT tests. As to SATs, College Board’s default position when you request that any SAT or subject test be sent is to send all SATs and all subject test scores it has for you but you can exercise score choice and eliminate any test or tests you do not want sent and, if you do so, those will not be included in what College Board sends to the college, and College Board will send nothing that even hints that you ever took the withheld tests.
Even if you exercise score choice , you may still have a risk that college will get all your test scores. This depends on what your high school puts on your transcript. Many high schools put all your test scores on the transcript sent to colleges and thus you need to check what your high school does.
As to whether you can withhold scores depends on the particular college and you should obey any rule of a college that requires you to send all scores. However, contrary to what many may believe, there are only a small number of colleges, 20 total by my count (12 if you count the 9 UCs as one) that are anti-score choice and have any kind of requirement to provide all scores. Moreover, what those actually require varies. For a list of those colleges and their requirements see my post in this thread http://talk.collegeconfidential.com/college-admissions/1781724-sat-subject-tests.html#latest