The following answer — on the topic of choosing a school with a proper Jewish atmosphere for the children — gives a glimpse into the way things worked in the mazkirus, the Rebbe’s secretariat.
There were “standard” letters (sometimes called “Prati-Klali”) that were often sent as a reply to individual people, to which the Rebbe would add a line or two of more “individualized” information in his holy handwriting on particular matters when it was submitted for signing.
Sometimes, as in this case, the Rebbe wrote an entire postscript and sent it back to the secretariat to be translated and typed up.
Here, the PS, translated and typed on the original letter, was submitted for the Rebbe’s review, after which a new letter was probably prepared, signed and sent off.
במענה לשאלתה – צודק בעלה שי’ שעיקר גדול בחינוך ילדים שילמדו בבי”ס [=בבית ספר] שאוירתו יר”ש [=יראת שמים] וכן בנוגע לדירתם ואפילו בנוגע לדירת מבוגרים וכדאי לוותר בשביל זה על כמה ענינים.
P.S. In reply to your question — your husband is right that a basic requirement in child education is that children should learn in a school whose atmosphere is permeated with Yiras Shomayim; the same is true in regard to residence, even residence of adults; and it is worthwhile to forgo many things for the sake of the above.