If you feel very strongly about this, I'd suggest writing a letter to the teacher advising him/her that you want your childs SAT's scores to remain private.
Schools have a duty to respond back to any written letter.
In my experience parents usually receive a positive outcome from writing in, probably more so now, as this letter will be seen as evidence ofsted can view and can question. Therefore it can be viewed as how the school is responding to parents (stakeholders) issues.
At our school children will gossip, and so scores are found out even though results are only given to parents in the end of term report.