When Mayor De Blasio was elected he announced there would be no more letter grades used for schools. Bloomberg released the final set in November 2013. His view (and that of now-Chancellor Farina) is that those grades simplify the situation too much and do not reflect the true nature of the school.
As Chalkbeat NY posted yesterday, the letter grades are officially gone. As you can see below, the details provided are more holistic and require parents and students to read more about schools before applying. I, for one, agree with shift and look forward to seeing its outcome.