My child is only 3, so I have no BTDT advice, but I do teach 1st and 2nd grade math, so maybe I can offer a different perspective.

I know there are a lot of people on this forum who have been burned by "differentiation" and I understand their opinions on the matter. Here's how I see it... Differentiation can work for a gifted child, but it is rare and dependent on the teacher's attitude toward giftedness, the teacher-child relationship, rigidness of the curriculum (and ability of the teacher to work within this rigidity), and the spoken & unspoken rules of the school/district. I will also say that the larger the gap between your child's abilities and the average abilities of the class, the less likely your child is to receive adequate instruction. (You should also consider the gap between your child and the "lowest" child in the room, as the focus is often more on bringing up the "low" kids than ensuring progress for the "high" kids.)

Here's how I currently make it work for my 2nd grade classes (The same model works for 1st grade, but right now I don't have a wide range of abilities in my first grade classes. Just an odd year.)...

1. We typically start with a short activity or whole group instruction that I see as beneficial to all the students in the room. I try to keep this short (less than 15 minutes).

2. Seat work - next the kids do problems from the text, or another assignment. Often this is skill practice for my gifted kids, but if the class assignment isn't beneficial for them, I'll assign different work.

3. Small groups - while the kids are doing their assigned problems, I pull 4 or 5 kids at a time for small group work. Each kid gets different problems, so the "average" kid might be building 86 with base ten blocks and showing me how to change it to make 46... but a gifted kid might be building 1,862 and showing me how to change it to make 1,462.

4. Packets - when the kids are done with the daily assignment, they can work on a fun packet. My kids love doing math mazes that involve algebraic thinking. Often I'll make multiple packets. The majority of the class might get a set of mazes that deal with addition of numbers under 25, while the gifted child might get a set that deals with bigger numbers (or maybe multiplication if he/she is ready).

5. Homework - Not everyone needs the same homework, but it sounds like your school is already open to this (many are not!).

This is just an idea of how differentiation has worked for me. However, as I stated earlier, the larger the gap between your child and the rest of the group, the more difficult it becomes to provide instruction that provides meaningful progress (and some teachers are better at it than others). Your child is 2 years ahead in math, and that is particularly difficult for most 1st grade teachers because the students aren't as independent as they are in later grades.

Hope this helps!