This is similar to what Watchtower did in Mexico to maintain ownership of the kingdom halls when laws were passed that all religious buildings became state property for the benefit of the community.
TL:DR - This happened between 15 June 1943 to 1 April 1989 - no singing of songs, no collective prayers, no bible use in first call door-to-door - stopped being a religious society and became a civil education society instead.
Yearbook 1995 - Pages 212 to 213
You will recall that back in 1932 La Torre del Vigía de México had been authorized by the government. However, there were obstacles because of the restrictions that the law imposed on all religions. Objections were raised to the house-to-house activity of the Witnesses, since the law stipulated that ‘every religious act of public worship must be held inside the temples.’ For the same reason, objections were raised to our conventions in public places. This was a problem, because these conventions were constantly getting larger. Owning property also presented problems, because the law required that every building used for religious purposes had to become federal property.
For these and other reasons, the Society decided that it would be wise to reorganize, with a view to giving greater emphasis to the educational nature of our work. Therefore, on June 10, 1943, application was made to the Secretariat of Foreign Affairs to register La Torre del Vigía as a civil society, and this was approved on June 15, 1943.
With this rearrangement, singing at our meetings was discontinued, and the meeting places became known as Halls for Cultural Studies. No audible prayers were said at meetings, though nothing could prevent a person from saying an earnest prayer silently in his heart. Every appearance of a religious service was avoided, and truly our meetings are designed for education. When Witnesses in other lands began to call their local groups “congregations,” the Witnesses in Mexico kept on using the term “companies.” House-to-house visits by the Witnesses continued, and with even more zeal; but direct use of the Bible at doors was avoided. Instead, publishers learned the texts by heart so that they could quote them. They also made good use of the book “Make Sure of All Things,” which is a compilation of Scripture quotations on many subjects. Only on return visits and on studies (which were termed “cultural” instead of “Bible”) was the Bible itself used.
Yearbook 1995 - Pages 232 to 234
The organization of Jehovah’s Witnesses has always operated along the same basic lines in Mexico as in other parts of the world. Also, since 1931, the brothers have individually identified themselves as Jehovah’s Witnesses. Yet, for many years, in Mexico, it was necessary for the organization to function as a civil and educational society, as explained earlier.
In 1989, with the approval of the Governing Body, a letter was written to all the “companies” saying that as of April 1, we would be operating in Mexico as a religious organization. Afterward, in the June issue of Nuestro Ministerio del Reino (Our Kingdom Ministry), which was changed from being called Informador (Informant) de la Torre del Vigía, further details were given. From then on, the Bible would be used from door to door, and prayers would be offered at meetings. Later, we began to sing songs at the meetings.
You can just imagine the rejoicing this brought to the congregations! Tears of joy streamed down the faces of the brothers in the Halls for Cultural Study, or Study Halls (which now became Kingdom Halls), and at the conventions and assemblies, when collective prayers and singing began. Furthermore, direct use of the Bible in our door-to-door witnessing infused the brothers with increased zeal, made their work more effective, and gave them great satisfaction. Without fully realizing it, we had also established a foundation from which to defend our Christian way of life legally.