I don't quite understand. How is this developmentally inappropriate? I understand how reading certain books can be developmentally inappropriate even though the child is capable due to the subject matter, but math?
Does math need to be developmentally appropriate and what does that even mean in math?
No. It is not developmentally inappropriate. I live in the tech heavy Nor Cal area and it is not uncommon for kids to be accelerated to algebra level at that age. That being said, I know what she was talking about. Many educators are told that for "most kids", it is very confusing to move from a world of concrete and explicit numbers and computations based on numbers to "abstract computations". They are suddenly told that there is a number called "x" and they need to solve for it and find out what it is and they don't have the "abstract" thinking powers to grasp those concepts at the second grade level. And also that children cannot easily grasp the concept of the equal sign used to balance the RH and LH side of an equation.
Any child in elementary school can be taught how to compute "x+2" and how to solve simple algebraic equations using variables. I am not talking about gifted kids, I am talking about typical kids - give them some "balance math" type of problems to play around with for a couple of weeks and they will get the concept of balancing equations.
To answer your question: no, nothing bad will happen to your child if he is taught algebra now. It may be hard for the teachers and the admins of the school to find the resources and the time to do it , it may be hard on the child because of writing requirements, but, conceptually, if your child has mastered arithmetic, he can handle it. I have seen it being done.
Good luck.