In easyCBM testing we use only one probe but we have a few veteran teachers asking why we aren't using 3 probes as before. Why is it different now?

In a way, both groups are correct. There were two assessment programs that used easyCBM measures. They are easyCBM and DIBELS. It gets a bit confusing as both the DIBELS and easyCBM programs originate from the University of Oregon. The protocol for the DIBELS measures was to administer three probes and take the median score. This approach was taken due to variability in the difficulty of the different probes. With easyCBM, we have fine-tuned the measures such that the alternate form reliability is extremely high (as high as .98 - .99 correlation between alternate forms of the same measure at a grade level). Thus, for easyCBM, administering three probes is not recommended, as doing so doesn't give you a more reliable score -- and increases the amount of time students spend testing rather than engaged in learning activities.