Can you have a high IQ with poor working memory?
Having a high IQ with a lower working memory means that that child needs to learn the strategies that go with supporting the lower working memory. Now, the trick here is if his IQ is in the 90th percentile or above and his working memory is in the 75th percentile, his working memory is still way above average.
Working memory, in particular, is strongly correlated with intelligence in children and adults. When people perform better on a working memory task, they also tend to perform better on an intelligence task.
Characteristics of a Weak Working Memory
Individuals with poor working memory tend to have trouble planning, organizing, and carrying out daily chores such as running errands, because it requires mentally formulating a “to do” list organized by time and location. Study skills may also suffer.
Critically, we find that working memory at the start of formal education is a more powerful predictor of subsequent academic success than IQ. This result has important implications for education, particularly with respect to developing intervention and training.
They can, but it's not just that. It's that IQ is a very noisy measure of all intellectual talents averaged together, and some people with unimpressive general IQs can still be extremely talented in particular fields. Even such a stereotypically intellectual pursuit as chess only correlates with IQ at 0.24.
The interesting thing about the working memory profile of a student with ADHD is that they do not have difficulties in short-term memory. In a testing situation, they can recall digits, words, instructions, and spatial locations at the same rate as their peers.
90-109: Average.
While IQ typically measures the knowledge acquired by the student, working memory measures what they do with that knowledge. Working memory skills are linked to key learning outcomes, including reading and math.
Rather than there being a set limitation, working-memory capacity could improve through practice--suggesting that those with working-memory problems could improve their capacities through repetition.
Yes, there are at least two types of memory problems, working memory and long term memory, which can lead to difficulties in learning. Problems in working memory can lead to difficulties in learning because the individual may have less space in working memory for organizing and integrating new skills or knowledge.
Why does my child have poor working memory?
Developmental and intellectual disabilities like ADHD, autism, Down syndrome, Rett syndrome, and developmental language disorder commonly cause memory problems. Though some of these conditions may affect long-term and visual memory, they most often disrupt working memory.
The results indicate that the basic modular structure of working memory is present from 6 years of age and possibly earlier, with each component undergoing sizable expansion in functional capacity throughout the early and middle school years to adolescence.

Students with specific learning disabilities have average to above average intelligence but may have difficulties acquiring and/or demonstrating knowledge and understanding content.
While young participants mostly did the best on the number-to-symbol coding tasks, with a peak age of around 19 to 20 years old, working memory peaked between the mid-20s and mid-30s, before starting to slowly decline.