If you can, begin writing your comments as students achieve their goals. The more that you can do before the frenzied period of report writing begins the better, be kind to yourself and lighten your own load. My advice would be to have a Word document at the ready, so that you are always able to add to it as you go.
Evidence of learning
Make sure you have the evidence of student learning. If a parent or administrator, Principal or colleague should ask you what that student did to achieve the goal, you have the physical evidence available. Even if your evidence is an observational checklist, that's valid evidence. Don't put anything into a report that you cannot prove.
Enter the relevant due dates in your diary and work backwards, to determine when you really need to be writing. Then, set aside a few weekends to focus on it. It’s really hard to write mid week whilst still teaching. I find writing in a block allows you to get into the swing of it and to write good quality comments. I also have colleagues that refuse to use their weekends - quite right too. One colleague prefers to stay later for a couple of weeks, so that her time at home is completely separate to work. Do what works best for you, but ensure you plan - it's the only way to keep to time.
Missing a deadline
If you think you are going to miss the deadline, speak to your line manager early. They are very forgiving if you give them fair warning and will often agree to proofread or print your reports last. You may even be given more release time to complete your reports.
Language, tone and content
Ask a colleague
Don't be afraid to run a comment by a colleague if you are feeling uncertain about its content. This is a good idea if you are struggling to be positive in a report for a student that you don't have a great relationship (despite what people think we should be, it's impossible to like everyone and you won't like every student that enters your classroom).
Editing and Proofreading
As you write, don’t worry too much about editing and proofreading. Get your thoughts down first. Set them aside for a few days before you begin editing. Edit content first, then proofread grammar and punctuation second.
When it's all over
Have reward ready for when you have finished! Celebrate with your favorite relaxation or celebration activity - youve earned it, well done :)