My friend Ann Ferren told me this story about a science faculty member who was continually frustrated with how badly his students wrote lab reports. Each week a new crop of poor writing would be handed in, and he would spend way too much time writing his comments in red ink all over them. But the writing failed to improve.
He then tried the following:
a) He told them he really cared about their writing
b) He distributed the criteria he was using in grading (this is sometimes called a 'rubric')
c) He told them that as soon as their writing earned an "A", they would no longer be required to turn in lab reports.
The results were wonderful.
One quarter of the students got "A"s on their first report. Another quarter of his students got an "A" on their second report. Pretty soon he was saving time and only coaching students who genuinely had problems with writing.
PS. Quite a few students continued to write the reports without handing them in; by writing a genuinely good report, those students has seen how writing a good report could help them learn from the lab work.