* State/Country Laws: Each state (in the US) and country has its own regulations regarding grade retention. Some may have limits, while others may leave it to the discretion of the school or district.
* School District Policy: Individual school districts often have their own policies that may place limits on retention or outline specific criteria for when it's considered.
* Individual Student Circumstances: In some cases, a student might be held back multiple times due to extenuating circumstances like prolonged illness or significant learning disabilities. Other times, repeated retention might lead to a different educational path being recommended.
In short, while there might be informal or practical limits (a student might eventually age out of the system or be placed in alternative programs), there's no universal legal or regulatory number.