YES! Both programs are designed for 50-55 minute sessions. But RY and CAST work in different ways.
Let’s look at RY first. Since RY is a school class, it needs to follow the bell schedule, whatever that may be. Sometimes schools have as little as 45-minute periods, sometimes as much as 75-90. If an RY class is scheduled for 3rd period, which meets on a block schedule (e.g., Mon, Wed, Fri for 80 minutes), you can combine two RY lessons into each class session. For those of you who are familiar with the Anatomy of an RY Lesson, you would start at the beginning (Check-In) and teach all the way through one lesson; then start the next lesson at Big Ideas and teach through that lesson. It is wise to allow the students a “brain break” at some point, perhaps midway through.
What about CAST? If you are implementing CAST in a school (which is only one of many appropriate settings), you simply keep the students together for the length of the CAST session. If you complete the session within 55 minutes, then you can send them back to class for the remainder of the period! Some schools prefer you to pull CAST students out of class for the latter part of a period, which allows them to be present for some of the lesson and get their assignments before leaving for their CAST group.