I find it a shame the public schools are so inflexible and like to live within a box. I have fought your battle many times and won some and lost others.
As a result we have moved schools every couple of years and I have 4 of them currently in 4 different schools. It has worked well for our family and allowed them to accelerate forward each and every year.

You may want to look into Laurel Springs Academy (https://laurelsprings.com/). They have a gifted program starting in middle school. I have an 8 and 10 yr (3rd and 5th) grade that used them for 4th math over the summer and 6th science. They are accredited and when comparing content they exceeded the content requirements for both my kids home schools. My 8 yr is in a private gifted school (Fulton Science Academy Private school) and daughter 10yo is in Gifted Magnet Charter Public school (Kittredge). Both schools accepted the summer school credits and course accelerated them. Both kids started school this week and split their day between 3rd/4th/5th and the other 5th/6th/7th. The principals for both schools were really impressed with the online program. It is affordable, rigorous, easy for even an 8 yo to work through the course and recommended on many gifted websites for an online program. I believe they do rolling admissions so you are not too late.

There are other summer options but they are GA specific or require you to apply much earlier. Good luck with Laurel Springs. We were very happy with our recent experience and will use them again.