I have not retained.
You have to do what is best for your child. If it is in her best interest, then you have to do it. As parents, many of us have done things that brought a little distress to our children, but if it is what we truly believe is the best, then we do it and move on.
So if your 10% doubt is based on distress and embarrassment, do what you have to do and move forward.
On the other hand, is it possible to get assistance for your child over the summer? My daughter was not the best student in 1st grade. She wasn't failing and didn't have any below average grades, but I knew she was struggling and the school suggested a reading program.
I put her in Kumon and by the 2nd grade conference (October), she was 6 months above grade level for reading and by the 2nd trimester, she had all 3's (top grade). Initially, I only put her in the reading program, but that helped her in many different areas. She advanced in her reading comprehension, which is needed to understand the instructions for your assignments. I just added math to her program about 3 months ago. She said she was a little slower than the rest in school and we added it. After talking to the teacher, she said that wasn't so, but I happy we added it.
In my view, the school has a curriculum to follow and meet. If your child does not learn, the teacher has to move on. Not to say they won't help them, but at that point they are already behind the eight ball. It is very easy for a child to find themselves in that position.
If you are able to wait to make your decision and able to find a reading/math program, put your child in and see if it helps. It proved to work for my child.