Implementing one module per week would be the furthest spacing ETR's adaptation experts would recommend. Many of these programs were originally developed for and implemented in community-based settings within a concentrated time frame. This was largely done for retention and logistical purposes, as it could be very hard to get the same group of youth to attend consistently over a longer intervention. Concentrating the information into a shorter time period helps ensure that the youth retain the learning and that the information and skills build from one module to the next, especially in community-based settings, where it is often more difficult to retain youth over a longer period of time. For example, Be Proud, Be Responsible was originally implemented as a full one-day workshop, although the developers do believe it can be implemented in six separate sessions as well.
School settings tend to have better retention, since the students are there every day, so spreading out to once per week if needed should be OK in that context. The identified risk with spreading out the content over a longer time span than recommended is that learners may forget material from the previous week and need additional time for review. Facilitators would need to be vigilant about checking whether students have retained material from previous sessions before moving on, and might even want to quickly review key information that will be relevant to the current session if there’s been full week between meetings.
If you carefully maintain the other core elements of the program and manage to keep the retention (both of students and what was learned last session), teaching one module or lesson per week could be an acceptable adaptation, particularly if attendance by all students can be guaranteed for all sessions.