Unfortunately, your observation is common among parents of gifted kids.

In USA public schools, there is a movement toward Equal Outcomes, also known as closing gaps between high performers and low performers. This includes capping the growth of students at the top. Teachers and schools are increasingly evaluated/rated/ranked on closing gaps and achieving equal outcomes. USA public school teachers who do not produce equal outcomes in their classes (data collection shows persistent gaps between high performers and low performers) may lose their jobs.

Here is a brief roundup including where this movement comes from, and a few of the grading practices to watch for as they may commonly be used to achieve equal outcomes:
- data collection is used to force equal outcomes
- ushered in by common core
- educational plank of party platforms
- rationing opportunities
- Nature versus nurture
- supplanting gifted students in "Gifted" programs
- replacing the classics with anthologies
- Grading practices (which tend to produce equal outcomes)
- list of grading practices
- policies which lack transparency
- requiring students to list new vocabulary words in the reading material, when there are none
- collective grading

A few brave souls still help raise awareness that gifted pupils have different educational needs, and that meeting these needs is NOT "elitist."
- Counterpoint statements
- The Gifted: Left Behind?
- one-size-fits-all

For continuing growth and development, kids need:
1) appropriate academic challenge
2) true peers
For typical kids, these needs may be met in a general ed classroom, however for children with higher IQ/giftedness, these needs may not be met without intentional effort in providing advanced curriculum, and grouping for instruction with academic/intellectual peers.