In 3rd/4th grade I had a rough time. I had strabismous (sorta like lazy eye but not) and no I don't know how to spell it. I was taken to an optometrist instead of an opthamologist (don't know how to spell that either) and was basically given horrible advice that made it so I have no depth perception then, now, and very little chance of getting it back (although they are making strides every day and I read this great book called "Fixing my Gaze"...my problems were nothing compared to this author).

The eyesight issues aside...here are the problems that I had throughout the years:
1. Eyes gave me headaches which made me grouchy and unwilling to read
2. I was considered a "good kid" and so was seated next to "bad kids" in an effort to improve their behavior...I was nagged/bullied continually through the year. Though my personality was such that I wasn't traumatized or in tears each day (I was pretty good at ignoring it and my feelings are hard to hurt), it was just very exhausting to always have to deal with being nagged relentlessly
3. I had stellar grades and test scores, but we had just transferred and I was not in the appropriate honors/gifted classes and was really bored. I day dreamed through most of class because if I paid attention the tempo was too slow and I would get frustrated.

It was just a very hard and frustrating year. And different personalities will react differently to these types of problems.

Yes, check the eyes, get a surgeon specializing in pediatric issues not just an optometrist

Ask who she sits next to at school. Do they get along. Does she have friends, has she had any issues with a friend. (One of my schoolmate's worst years was the year her best friend died...).