My understanding is that to carry out a multilevel (model, a rule of thumb is that around 12 level 2 units, or groups, is needed. 

**Is this a helpful rule of thumb, without additional information**? What is this based on? What considerations, technical and otherwise, should be considered?

I searched, and this doesn't seem to have been asked as a question, at least as the focus.

*Note*. The data I'm working to analyze is from around 200 students grouped into one of 10 programs. The number of students in each group is about equal (around 20 per program).