Fortunately, this old paper is still pertinent. It debunks several myths used to avoid subject acceleration:
Originally Posted by paper
In Search of Reality: Unraveling the Myths about Tracking, Ability Grouping, and the Gifted
(Ability Grouping and Acceleration) Ellen D. Fiedler; Richard E. Lange; Susan Winebrenner.
Roeper Review
, Spring 2002 v24 i3 p108(4)
Full Text: COPYRIGHT 2002 The Roeper School
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Myth #1: Tracking and ability grouping are the same thing.
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Myth #2: Ability grouping is elitist.
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Not all students have the ability or desire to participate on a varsity sports team, yet I have never heard any school official argue that singling out talented athletes for team membership to the exclusion of others is elitist. In fact, school districts and local community agencies go to great lengths applauding these athletes' efforts and supporting them in their development.
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Myth #3: Ability grouping inevitably discriminates against racial and ethnic minority students.
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Myth #4: Gifted students will make it on their own; grouping them by ability does not result in improved learning or achievement for them.
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Myth #5: Providing heterogeneously grouped cooperative learning experiences is most effective for serving all students, including the gifted.
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Myth #6: Assuring that there are some gifted students in all classrooms will provide positive role models for others and will automatically improve the classroom climate.
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Note: "ability grouping" may also be known as cluster grouping by readiness and ability.
The paper is available on wayback machine, internet archive, here.
Link - https://web.archive.org/web/20170918201400/http://www.casenex.com/casenet/pages/virtualLibrary/gridlock/groupmyths.html

Adding a link to related discussion threads, pertaining to limiting student ability to move ahead in math, on the West Coast of the USA:
1) in the San Francisco Unified School District: Math test doesn't add up
2) for the entire State of California: http://giftedissues.davidsongifted....ts_needed_urgently_re_CA.html#Post248829