Developing Consensus and Overcoming Obstacles in My Action Research Project

This week has been great in terms of getting feedback on my action research project.  The proposal was approved as is so as of now I don't need to repost it, but there were several very helpful suggestions made in terms of how to effectively implement a word wall in the classroom - strategies to use, examples of what worked and didn't work for other teachers and suggestions for overcoming problems with day to day use.  The biggest challenge I see now is how to evaluate the success or failure of the project.  If I look at only the district assessment or End of Course scores how do I know how much impact the word wall actually had on the outcome.  I could do some kind of vocabulary test, but I would want to make sure it is an authentic assessment.  I will be documenting informal assessments, but I don't feel like that is enough.  Any input or suggestions would be greatly appreciated.