There are two things parents typically want to know about their child's situation in your class. One is how the child is doing (the grade in progress) and the other is what the child can do to improve his or her standing in the course.
I think they're entitled to good answers on both issues. And I do my best to provide as much.
The homepage of my website (http://phyz.org), I have a link to the latest grades in progress. The grades document is a PDF "print" of the same grades I post in the window of my classroom. They are listed by period and coded by student phone numbers. Parents can access this information wherever they have access to the Internet.
During the semester, the grade information is provided in great detail. Speciifc test scores and lab scores and various percentages, etc.
But at the end of the semester, I list only the letter grade. This avoids the errant conversations that typically arise from percentage values that end in a 9. While the vast majority of students and parents understand how grades are given, a few do not. A student with a 79% will feel entitled to a B. Why? Because they were so close! No other reason is necessary. Again, these are few and far between. But not nonexistent.
Anyway, I also keep a list of suggestions for students who wish to improve their performance in the course. It can be found--in PDF format--here.