My usual novice class goes like this:
- warm-up and conditioning for 10 minutes
- MATWORK: practice a technique we already know for 10 minutes
- MATWORK: teach a new technique and practice it for 15 minutes
- STANDING: practice a technique we already know for 10 minutes
- STANDING: teach a new technique and practice it for 15 minutes
- matwork randori for 5-10 minutes
- matches for 10 - 15 minutes, including both standing and mat work
I might rotate the matwork and standing practice and instruction, but this is pretty much my regular routine. When I teach a beginning kids class I don't see a point in more than 20 minutes of free practice because they really don't know much to practice yet.
The same applies to judo. Just because you have taught something does not mean that your students have learned it. So .... every few weeks, I will have the free practice at the BEGINNING of class, right after the warm-up. I watch the students to see what I think are their weak points as a class. Does no one attempt a choke? Does anyone escape from a pin?
Then, I call them all together and explain that this is what I saw when I was watching them, and that is what we work on that day.
By the way, this is also a good plan for when you are asked to teach a clinic. People generally pay more attention if they know you at least have SOME idea about the judo they do rather than giving your standard dog and pony show you've given 450 times before.