a tale of two classes

I have had two observations done so far.  One was by my mentor in my high school science class.  He said I was doing a really good job teaching a new topic to the kids, establishing a good rapport with them, etc.  I was on cloud nine.  Today I had another observation by the middle school principal in my 8th grade class....it was a total opposite.  The kids were on their worst behavior.  He told me based on that observation he should recommend me for classroom management training.  I was upset but then I looked at it from a different perspective.  I know I'm not the only teacher who has a tough class to deal with.  I have several special needs kids in this class--behavior and learning problems.  I will have to come down a little tougher on these kids and do more to keep them engaged.  He may come observe my other 8th grade class which is better behaved.