There are lots of ways to learn and more variances than (a)phantasia for learning. I believe that there are very, very few things in school that are a near-impossibility for an aphant to learn/do, and those are along the lines of writing about poetry and stories that are supposed to invoke some emotional reaction, or cause some sight, sounds, or smells. If the assignment is how it affects "you" the student, then it is a problem. But, "what is the author trying to convey" should not be a problem. I believe most aphants don't know it, and shouldn't worry about it. I've found quite a few in various STEAMA careers (sci, tech, eng, arch, math, accounting).

As one with aphantasia, I found listening was challenge because I couldn’t visualize what was beging said, but visuals really helped. For example, when listening to a lecture, I would take notes, and my notes would include both words and pictures. Because I couldn’t visualize the pictures really helped with processing aspects of the lessons. And I still do this as an adult. In fact the guy who invented the Firefox browser reportedly has aphantasia, although before they coined the term. He was able to be very successful because he learned to draw out his ideas on papers and a white board. But visualization is honestly only one element of learning, and if you research/google learning styles, you will get loads of information on how different students learn and study advice for each of the different styles. I hope this helps you help your daughters with their education.