Some school advertise when it's time for such parent input, and some don't. Some offer guidelines, and some don't. Whether or not the path is clear, your input into your child does have an impact on placement. How you write and phrase the letter has an impact, too. You want to walk that fine line of collaborative, contructive content - and not step over into hover mode.
Letter? Or meeting?
Writing letters can be an effective tool as part of guiding your child's academic career, but they are not for every situation. Generally speaking, if your child has had a mostly okay year, a letter is what will work best. If your child has bigger issues in learning and/or socialization, a meeting would be more appropriate - and you likely already have it set up anyway
Early - but not too early
When should you write a letter about your child's placement? Check with your child's school and/or district to see if they have a policy on when they will accept letters. If they do, follow that policy. If they don't, at least a month before the end of the school is likely will give you and your child the most consideration - but not more than about two months.
Offer insights and goals
When writing a letter on behalf of your child's placement, offer insights into what has gone well in the current school year, and what hasn't. Is there an area you think your child needs particular help in? Are there areas were your child has excelled? Offering a bit of happy grease on the way to making suggestions or requests is a little political, yes, but it often does its job.
Mention realistic goals, too. A fairly specific target can be an excellent starting point for teachers and administrators to work with you on behalf of your child.
Don't make demands
Making outright demands is an almost sure way to not get what you want. Some school districts are clear on this and will tell you that requests for specific teachers or learning groups will not be considered. You may wish that your child have the same awesome 3rd grade teacher your older child had, but there are other factors the school is considering. Instead, try describing the learning environment you think your child will thrive in - and if it happens to match a desired teacher almost exactly, you may have more of a chance.
Edit, edit, edit
Writing is a process, and rarely is any writing un-improvable. Take time to write this letter and edit, edit, edit. Keep it to a single sheet of paper for the most impact and make sure every word counts. Have other eyes look at it to help make sure content, format, spelling and grammar are all correct. Sleep on it for several days. Give yourself a solid week to compose and refine this letter before sending it off. That way you can make sure the letter says exactly what you want it to say.
While writing a letter on behalf of your child for the coming year's placement is no guarantee that the year will be a perfect one, it's a step toward building a collaborative relationship with your child's school and teacher.
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