I teach courses in physics, astronomy and planetary science.
Often, but certainly not always, international students (and even some domestic students, for whom English is not their primary language), write worse than their domestic peers who have grown up with English.
For most assignments, I take up to a couple points off for negligence of spelling and grammar, depending on how bad their writing was. The point is to remind students that their writing should be professional. I never nit-pick about a typo here or there, but if there is a whole slew of them, I'll make a note and take off what would amount to be a few percentage points of the assignment's total score.
I'd like to give grace to those for whom English is not their primary language. At the same time, I need to be fair and grade equally. As it stands, I grade equally for everyone, but I try to give more feedback to those who need it.
Does anyone have any better ideas about how to do this?