Can My Son Sing a Christmas Song?

Shalom Rav Bar Chaim,
Two of my sons aged 8 and 6 attend public school in *****, NJ. Their music class (which is a required class) includes Christmas songs during this time of year. I have instructed my sons not to sing those songs, and to tell their teachers their religious beliefs forbid them from participating in any Christmas related activities. I found out today that my son’s teacher ordered him to sing those songs at a school concert, and then told my wife that she had done this with the support of the principal. The Principal later confirmed this to me over the phone, claiming that the songs’ lyrics have no religious content. (One of the songs is titled “Christmas is coming”.) I explained to him that the content is not the issue. If Jewish law forbids him from singing the song – regardless of its content – he should not be forced to sing it. It would be no different than compelling him to eat non-kosher food, even though the food has no religious meaning. The Principal said he would get back to me after checking with his attorney.
What I would like to ask you is as follows:
Ignoring all other considerations, is it permissible or forbidden according to halachah, to sing a Christmas songs that refer to Santa Clause, and stocking on the chimney, etc. but make no reference to the Christian religion?
If a song, as described above, contains the verse “G-d bless you,” is that considered a Christian reference?
Assuming these songs are forbidden by halachah, and the school won’t yield, is it permitted to pretend to sing the song (as part of a choir), or to stand still (without pretending to sing), or is one required by halachah to openly refuse?
Please respond as soon as possible, as this issue concerns possible avodah zara, and will not go away.
I thank you in advance.

I agree that your sons should not be forced to sing Christmas songs. I disagree that this has nothing to do with the songs’ content; if the content was innocuous there would be no issue.
It is probable that the principal and teacher sincerely feel that these songs are devoid of any religious connotation. They are entitled to their opinion. We are entitled to ours. In our view, which is rooted in a much keener awareness of such matters than one could reasonably expect of them, all Christmas songs connote, as the term implies, a Christian message, even if only subliminal and unintended.
Point out to the principal that when faced with the choice “The cross or the sword”, our forefathers chose the sword, for themselves and their children.
Your sons should be exempted from such classes. Freedom of religion includes the freedom not to participate in any activity which one finds objectionable due to religious sensibilities. This too should be pointed out to the principal.
If they are not exempted, continue to instruct your sons not to sing such songs. They may stand together with other children in a choir, but they should not mouth the words. If ordered to, they should refuse. This is by no means an easy thing for a young child to do; they will require your active backing and defence.
As a last resort, threaten the school with legal action. Hint at turning to the media. My guess is that they will back down. Start making legal inquiries in case they do not.
The most meaningful advice I can offer you is this: come home. This was Hazal’s forceful recommendation even when the situation was reversed. In the words of Rambam z’l (M’lakhim w’Milhamoth 5:15, 5:12 in some editions) quoting TB K’thuboth 110b:
לְעוֹלָם יָדוּר אָדָם בְּאֶרֶץ יִשְׂרָאֵל, אַפִלּוּ בְּעִיר שֶׁרֻבָּהּ גּוֹיִים; וְאַל יָדוּר בְּחוּצָה לָאָרֶץ, וְאַפִלּוּ בְּעִיר שֶׁרֻבָּהּ יִשְׂרָאֵל: שֶׁכָּל הַיּוֹצֶא לְחוּצָה לָאָרֶץ–כְּאִלּוּ עוֹבֵד עֲבוֹדָה זָרָה, שֶׁנֶּאֱמָר “כִּי-גֵרְשׁוּנִי הַיּוֹם מֵהִסְתַּפֵּחַ בְּנַחֲלַת ה’ לֵאמֹר לֵךְ עֲבֹד אֱלֹהִים אֲחֵרִים שמואל א כו,יט. וּבְפֻרְעָנוּת הוּא אוֹמֵר “וְאֶל-אַדְמַת יִשְׂרָאֵל לֹא יָבֹאוּ יחזקאל יג,ט.
Rabbi David Bar-Hayim”