We are in the process of changing our grading scale, no zeros, make-up work, retesting, etc. Input or what your school has done would be helpful. Research based would be the ke.
I teach in an elementary school and we have begun to make the switch to SBPR (student based progress reports) We know grade on a scale of B: Beginning D: Developing and S: Secure. It is a lot more work but I do think its made me look at my students with more detail.
What makes me laugh is the comment by many of our secondary ed. teaches we are preparing our kids for college when they refuse late work, retest, zeroes, etc. After talking to many of our collge students, the colleges seem to be kinder towards the learning of the material than strict grading policies. Colleges as long as they are getting our best students that are prepared for college level work.