This thread is based on an old post from May 02, 2016, with several updates. Various links discuss PROs and CONs of grade skipping, including single subject acceleration (SSA), multiple grade skips, and the opposite of grade-skipping: red-shirting. This roundup makes it a bit easier to find discussion threads on acceleration, since each discussion may be found using different topic search terms, and therefore it can take quite a bit of time to collect the range of views expressed.

Grade skipping (also called whole-grade acceleration) is a frequent topic of discussion on the forums, as it is such an important decision. Roundup of advocacy links here.

No doubt others will share their stories, but I'll begin by saying that because each child and learning environment is unique, every case is different. The Iowa Acceleration Scale (IAS) is a tool made to help evaluate the appropriateness of full-grade acceleration in a given set of circumstances. As there is good and bad in everything, there are both pros and cons to acceleration. Many old threads discuss the ups and downs of acceleration. Here is a link to one thread which contains links to several other discussion threads on acceleration.

Here is a quick summary of those links, an acceleration roundup, in case it is more convenient to read them listed in one post:
- Grade skipping tradeoffs (2014) discusses possible drawbacks, downsides, and disadvantages to grade-skipping.
- Kindergarten, experiences with grade-skipping? (2008)
- Effects of Early Grade Acceleration (2015)
- Accelerated schooling - skipping a year (2013)
- Skip a grade? (2014)
- old post (2013) discussing acceleration (Tamara Fisher archives: Unwrapping the Gifted)

- More old threads on acceleration:
Fears of skipping grades (2007),
EG/PG and not accelerated? (2008),
The other side of the coin (redshirting) (2008),
skipping up a grade (2008),
Grade skipping - revisited (2009),
Grade skipping fears (2009),
Telling friends about grade acceleration (2009),
We can't let the kid skip be-cauuse.... (2010),
Possible Grade Skip for Child (2011),
Any PG kids never skipped a grade? (2011),
Out of options, hoping for the best (2012),
Grade skipping and STEM accomplishments (2012),
Against Accelerating the Gifted Child (2012),
What warrants a skip? (2013),
Skipping/Red-shirting (2013),
Help: Multi-grade skip possible...... need advice (2013),
Knowledge gaps with a double grade skip (2013),
Leveling Out (2013),
Plateauing (2013),
grade acceleration? (2014),
If you or your child skipped a grade (2014),

Subject Acceleration (2015) mentions IQ,
School Administrators as Politicians (2015),
What to say when students ask about a grade skip (2015).

- Newer discussion links on this topic include:
Anyone choose NOT to accelerate? Is that crazy? (2016),
Grade skipping resulting in early college (2016),
Adding a link to a thread on early college (2016),
IQ scores for a two year skip? (2016),
article mentioning acceleration - SMPY study (2016):
Acceleration is common in SMPY's elite 1-in-10,000 cohort, whose intellectual diversity and rapid pace of learning make them among the most challenging to educate. Advancing these students costs little or nothing, and in some cases may save schools money, says Lubinski. “These kids often don't need anything innovative or novel,” he says, “they just need earlier access to what's already available to older kids.”
Thinking of skipping a grade? (2016),
options for 15 year old after high school (2016),
For BTDT: Anyone decide not to accelerate? (2017),
Transition Meeting/Grade Skipped/Advocacy Skills (2017),
Grade skip vs gifted program (2018),
Grade Skip - Yes or No? (2018),
Cold feet with upcoming grade skip (2018),
College at 16 (2018),
college at 15 before high school graduation (2018),
14yo going to college - advice and tips please (2019),
Full-Grade Acceleration to 1st Grade Issues (2019),
Child reluctant to grade skip (2019),
Expected grades after grade skips (2019),
Exceptionally gifted children by Miraca Gross (2020),
How bad is the social aspect of grade skipping? (2020),
The (Gifted) Kids Are All Right (2020),
Math Test Doesn't Add Up - single subject acceleration (2021),
Acceleration in high school (2021).

- a few thoughts about gym class or physical education (PE):
Grade skipping tradeoffs - denying accelerated students their earned awards (2014),
Grade skipped and facing middle school (2015),
Grade skipping and sports (2015),
Subject Acceleration and Changing Buildings (2016).

There is also this bit of insight from an old post (2013):
Originally Posted By: ZenScanner
they can accelerate as fast as they can, but school and online videos are rarely going to offer the direct metacognitive support for the secondary skills they did not give themselves time to develop (such as sanity checks and rereading problems).
Curriculum focused standardized tests are more often going to focus on the direct testing of specific element knowledge and application. They can become poor indicators of actual mastery that would include the full range of secondary skills.

Here is a link to a post (2016) which seems to understand very well why many students (and their parents) choose full-grade acceleration. In addition to expressing understanding, this post also mentions the research on acceleration:
Originally Posted By: aeh
I have first- or second-hand knowledge of an unusually high number of acceleration stories, including many radical accelerants into early college, and it is clear to me that a significant number of those individuals would have suffered loss or injury to important aspects of themselves had they not been accelerated. The costs of acceleration were well worth it for them. Those observers who believe the costs -were- too high generally have not grasped the severity of pre-acceleration psychic pain they were experiencing. These are the kinds of data captured by the longitudinal research on radical acceleration.

Here is a link to a research paper, The Socioaffective Impact of Acceleration and Ability Grouping - Recommendations for Best Practice (2007), mentioned in a thread called Looking for information about social development.

Here is a link to a post which mentions potential costs of NOT accelerating (2016).

To help minimize the numbers of persons who suffer the lack of appropriate acceleration, the Acceleration Institute has conducted and presented research showing the generally positive results of a grade skip, especially when factors listed in the IAS are proactively considered/weighed in the decision-making. Two things may work against broader acceptance/adoption of acceleration:
1) Entrenched thinking of "peers" as being those of the same chronological age (rather than intellectual/academic peers)
2) Common Core has ushered in an era of extensive data collation enabling the evaluation/rating/ranking of schools and teachers based on achieving equal outcomes among their student populations. Closing achievement gaps to gain a positive evaluation/rating/ranking may often involve capping the growth of students at the top

Resources:
1. Studies conducted by the University of Iowa on the subject of acceleration,
2. Acceleration Institute,
3. A Nation Deceived (circa 2004),
4. The ten-year follow-up to A Nation Deceived: A Nation Empowered,
5. Iowa Acceleration Scale (IAS). The Iowa Acceleration Scale (IAS) is described on Hoagies Gifted Education Page here and the actual IAS, 3rd edition, is sold by Gifted Unlimited, here.
6. Gregory Park dissertation (2011)
7. Vanderbilt - When Less is More: Effects of Grade Skipping on Adult STEM Productivity Among Mathematically Precocious Adolescents (2013)
8. Presentation of Prof. Dr. Nicholas Colangelo at Radboud Universiteit Nijmegen, Netherlands (youtube video, 41:05, published Nov 2013)
9. NAGC webinar - Acceleration: Making Informed Decisions, PowerPoint slides (2015)
10. Accelerate Illinois, report presented by Illinois Association for Gifted Children (IAGC), 2017
11. Article on Davidson Database (A10313), excerpt from A Nation Empowered, listing 20 types of acceleration
12. Article on Davidson Database (A10487) including international guidelines for acceleration.
13. NCGRE (UNCONN) Key Findings include findings on acceleration (unfortunately, the infrequent use of subject matter acceleration)
14. NOTE: If a link is broken or if the linked contents have changed (such as occurs with an update or a redesigned website), then try looking for the link in the "WayBack Machine," internet archive.