From what you say, it sounds like your daughter may have “dyslexia,” or perhaps a simpler problem with “visual processing.” Reading problems are very common, both among children and adults. If you think about it, reading is a very unnatural thing to do. In fact, no one read until about 5000 years ago when written language began to develop! So it is normal to have difficulty with it.
There are many approaches for addressing issues with reading, depending on the underlying causes. Sometimes a child simply needs glasses. Other times the issue is with “visual discrimination,” with rapidly discerning the small differences between little squiggles such as “p” and “g,” “d” and “b,” or “x” and “+”. Often there is an issue with “auditory discrimination,” with tracking the rapid changes in speech sounds. The first step is relating those phonemic units to letters and syllables in words. Commonly, the deep source of reading problems is a difficulty in relating visual processing to auditory processing, to rapidly associating the shapes of squiggles on a page (e.g., letters, syllables, words) to the sounds that are the basis of the oral language one learned as a young child before later learning to read (visual language).
This probably seems very complicated, and perhaps overwhelming. But really, most reading issues work out over time. What is important is to understand it is not the child’s fault, and that reading and related school activities can feel embarrassing and stressful for a child – so she needs extra understanding and nurturing, extra compassion and kindness.
I suggest you speak to the people at your daughter’s school and see what resources they can offer. By law, even if a child is going to an independent (private) school, she has access to the services of a public school if she has a significant learning issue. Informally, her classroom teacher might make some adjustments. More formally, the school could form a “student study team” to coordinate their efforts for her. Most formally, your school district could develop an Individual Educational Plan” (IEP).
Additionally, it is often very useful to work with people privately, outside of the school system – people who work for you and who are accountable to you – such as a psychologist, who can administer tests to assess what is actually happening and what the causes are, or a learning specialist, who can work with the child individually. There are helpful literacy programs, such as Slingerland or Lindamood-Bell.
As you take these actions, step back every few months and try to evaluate whether they are helping. In a hypothetical example, if your daughter has a general intelligence in the top fifth of children her age but her scores on reading tests are usually in the bottom fifth (and this doesn’t improve over time, even if her reading ability improves), the large gap between her ability (general intelligence) and performance (reading skills) is not getting any narrower. When there is a lack of improvement over several years, everyone involved needs to pause and figure out what to do differently, and not just keep doing the same old things.
At home, it usually backfires to put pressure on a child related to reading. Be sure to make reading fun rather than a scary and stressful chore. When reading with her, you could gently encourage her to try to sound out some of the words, almost as a kind of game, but if she can’t quickly figure out a word, just tell her what it is so she can get a sense of the sentence as a whole, the paragraph as a whole, and the story as a whole. Reading should be rewarding – otherwise she will not be motivated to make the effort to get better at it.
Most of all, stay focused on big goals such as a love of learning, feeling good about herself, developing abilities that are not related to school (e.g., understanding others, music), and a comfortable low-stress relationship with her parents. These are more important than being a good speller or a fast reader. Sometimes people chase improvements on test scores that come with great costs to overall well-being and relationships. There are many successful, intelligent, and happy adults who function very well in the world, and who also continue to find that reading large amounts of text is slow and effortful, and who find other ways to get their information. Keep reading in perspective and take the long view, rather than getting trapped in fixating on short-term goals, such as this week’s spelling test.