Year End Assessment

As we come to a close to the end of our year we as teachers need to be able to focus on assessment for the students in our classrooms.  In my classroom we take each child and assess them through testing individually to determine where they are at in their cognitive development.  I know that this is a state way to test the children, but to fully assess the students I don't believe that it works for every child.  Though we assess the children throughout the year I believe that it is inaccurate to evaluate the students based on one test.  We have very high and low functioning students in our class that deserve to be assessed fairly with regards to their cognitive development.  I feel that when the students are asked to step into the hallway by themselves to be tested it puts a high amount of stress on the children that in turn may have them not perform at the level that they are capable of performing at.  My question in turn is how do we assess students in a way that is comfortable to them and still meets state standards?  Is it possible or is it an unrealistic dream to have children perform at their highest level stress free?