Lots of children with sensory processing disorders also have retained infantile reflexes, which can make sitting still in a classroom almost impossible. There is also a link between sensory processing disorders and cerebellar dysfunction, which can likewise make sitting still difficult. Children who have poor proprioception (often an aspect of a sensory processing disorder) frequently move constantly just so that they can be aware of where their bodies are in space. If they don't move and fidget, they have a hard time balancing or telling what position their body is in. Stimulants won't help this. A sensory diet of frequent heavy work, "buzzing and brushing", and deep proprioceptive input, along with activities that help reintegrate infantile reflexes and improve balance and coordination can help many children with these issues be better able to sit still.
ETA: Perhaps sharing
this information with the O-G tutor will make her back off a bit on her insistence that your child needs to be still while learning...
