Our son had mediocre to poor grades at a private school in K-5. He was an eager student and turned stuff in, but his work was poor quality with loads of mistakes. The teachers did not really express concern, just kept telling us “get him to read more on his own” or “he should study more.”
After he finally started public school in grade 6, he took a standardized test and was 15th percentile in reading. This triggered a more complete evaluation and they found out that he couldn’t physically focus his eyes well enough to read books, or read his own handwriting to do math problems. He also had cognitive visual processing issues that probably came from not addressing physical vision issues early enough. He needed vision therapy and special glasses. Everything changed once the visual issues were sorted out and he became a top student after that.
We were lucky that our public school had excellent resources to evaluate and assist us. The private school had nothing. The whole process really drove home to me how a student with poor academic performance might just have some very specific barrier that was not discovered or addressed. In my son’s case, standardized testing ended up being the key to finding out what was wrong.