The CGS program has been able to hide its heterodoxy through the lack of a single, universal curriculum. This is one reason why the program has never been approved by the USCCB. Only very general parts are open and presented to the public. The specifics of what is taught in each class vary among the different catechists and class trainers.
Only a general guide and curriculum is presented for all to evaluate. The specific content and doctrines taught in each class are stored in the 'album pages' and vary from catechist to catechist. All CGS catechists attend classes to be trained to teach CGS and learn the CGS ideology and method. It is here that each catechist records his or her album pages by hand as they are instructed by the CGS group-leader. Since these album pages are particular to each instructor, some are orthodox and some are laced with personal agendas or theological errors. This is a critical, fundamental problem of CSG.
Another problem is the fact that the curriculum is always changing. Certain doctrines need to be taught to children and certain stages; yet CGS is constantly changing what is being taught.
"As Catechesis of the Good Shepherd catechists, we are continually writing and refining our albums that contain descriptions of each presentation we offer to children, including its sources and doctrinal content. Each catechist’s album is in continual revision and there is no complete set of album pages that is published." https://www.cgsusa.org/wp-content/uploads/CGS-Conformity-with-the-CCC_RC-Tradition.pdf