Onthegomom, I don't understand why you feel "compelled" to send a note or what you want to achieve by it. I think as it is it is likely to make the teacher feel patronised. IME the kind of playing with different ways to do sums is not something that is unique to gifted children, it's a normal and perhaps essential part of developing number sense, so it's a bit "off" to write about this as though it's unique to your child.
Is your main concern that they're not seeing what your DS can do? In that case, can you perhaps more neutrally send in stuff he's done recently, maybe without comment, maybe semi-regularly? It's always likely to be more effective to show than tell, I think.
Also, what is it that makes them think your DS is not developmentally ready for multiplication? If you don't understand what they're seeing there, you might want to ask. Getting a sheet of multiplication sums right does not rule out there being some truth in what they say, since understanding multiplication is not all-or-nothing.
An example: my DS learned to do 2-digit by 2-digit multiplication, could sensibly explain what he was doing, seemed to understand it perfectly... and then unlearned it. Refused to do it for weeks, complained and made mistakes that looked like basic conceptual errors (e.g. would multiply the units digits together, and multiply the tens digits together, but not include the other summands) if I tried to press him. Then started to do it again better, and jumped to beyond where he'd been before (e.g. working out areas of circles). I'm aiming to facilitate but not drive his learning (not always easy though!) so as far as possible I stood back and watched this whole process, but it was deeply weird, and I still can't really understand what went on. It must, though, have been in some sense that he understood multiplication so far and no further, and then needed to go backwards to make a leap. Getting to the point finally: if someone had come to me and said just after he'd got 100% on his ALEKS level 4 final assessment that he didn't understand multiplication, I'd have said they were off their rocker, yet there proved to be a sense in which they'd have been right. It's possible that this process that looked mysterious to me would not look mysterious at all to someone who had more knowledge and experience of how mathematical concepts are learned. Perhaps it's worth asking what they mean about your DS, just in case there is some sense in it!
