Hello. My middle son sounds similar to your son with similar learning rate and love of learning and is now in 5th grade- I will share tips I know that have been beneficial:
-Get an independent evaluation completed or request an IQ from the school psychologist. We did this and it has been helpful in advocating
-Speak with the principal prior to his enrollment and request a teacher that is prepared for a high level of differentiation
-Advocate every year for him to be placed with the best teacher- this makes all of the difference
-Regardless of K or 1 the pace of the curriculum will always be way to slow. For this reason, we did the K and have advocated for as much differentiation as possible
-The district tried to have him skip last year (so 4-6th), but we refused. The extra year gives him another year of math in school, he has friends, is a smaller guy and for what? so he could plateau within a few months?
-My oldest is a senior in HS, the extra year does give an advantage on act, and I have been glad to have her at our house this extra 18th year, it goes too fast, I am glad she wasnt moving away a year sooner- you are smart to think of the driving and sports, they are a reality:)
-Consider single-subject acceleration. My son initially advanced 1 grade in math, but quickly reached a plateau- He is now 3 grades ahead in curriculum attending the middle school with a group that is on a track for 2years ahead so he is only with kids 1 year older, but on an 8th gr level (prealgebra)
-The district tested him for this placement and all test scores indicated that he should be there, but they wanted us to sign off one placement lower for their scheduling ease- Fortunately we knew that the test scores indicated this and were able to ask the right questions, dont be afraid to ask,- we did and he is doing outstanding and is clearly in the best placement- always be informed
-Request that he be paired with another student at his level if one is available. My son has this and it is the greatest gift and blessing of all. many schools look to separate the gifted into equal numbers- research tells you they need to be together, advocate for it
-I work in his school and I know that the teachers have their best interest at heart, so I am not "demanding" , but I do offer the types of info you shared with each teacher of things he likes and how he learns- and then we do advocate because if you dont ask and its not happening chances are it wont
-ask for pre-tests of curriculum, when he passes that ask for extentions on his level
-Ultimately, we were not happy with public school during middle school and opted for private for our oldest. In the younger grades, public was better than pprivate for gifted. Now, our school is cutting the gifted program (I am going tomorrow to discuss this...) , but I am aware of the other local schools and their programming and will switch schools for my youngest if the programming is gone- stay informed- if there is a gifted school near you, take advantage of it, I wish we had that opportunity!!
Sounds like you have an amazing little guy...Good Luck!!