Changing permissions with PowerShell does not apply to children

I am combing the Internet and a few StackOverflow questions trying to figure this out. I may not have a better solution, but I think this satisfies the question. According to my research, Powershell Set-Acljust doesn't handle inheritance properly. The key to the code below is two things: an object System.Security.AccessControl.DirectorySecurityand using an alternative method to set the ACL $dir.SetAccessControl(). Children of the target folder (both folders and files) will successfully inherit the permissions attached to your target folder.

Call example:

$newACL=@()
$newACL+=New-Object System.Security.AccessControl.FileSystemAccessRule -ArgumentList @("MyLocalGroup1","ReadAndExecute,Synchronize","ContainerInherit,ObjectInherit","None","Allow")
$newACL+=New-Object System.Security.AccessControl.FileSystemAccessRule -ArgumentList @("MyLocalGroup2","FullControl","ContainerInherit,ObjectInherit","None","Allow")
Set-FolderPermissions -Path $Path -KeepDefault -ResetOwner -AccessRuleList $newACL

Functions:

function Set-FolderPermissions {
  # The whole point of this script is because Set-Acl bungles inheritance
  [CmdletBinding(SupportsShouldProcess=$false)]
  Param ([Parameter(Mandatory=$true, ValueFromPipeline=$false)] [ValidateNotNullOrEmpty()] [string]$Path,
         [Parameter(Mandatory=$false, ValueFromPipeline=$false)] [switch]$KeepExisting,
         [Parameter(Mandatory=$false, ValueFromPipeline=$false)] [switch]$KeepDefault,
         [Parameter(Mandatory=$false, ValueFromPipeline=$false)] [switch]$ResetOwner,
         [Parameter(Mandatory=$true, ValueFromPipeline=$false)] [System.Security.AccessControl.FileSystemAccessRule[]]$AccessRuleList)

  Process {
    $aryDefaultACL="NT AUTHORITY\SYSTEM","CREATOR OWNER","BUILTIN\Administrators"
    $tempACL=@()
    $owner=New-Object System.Security.Principal.NTAccount("BUILTIN","Administrators")
    $acl=Get-Acl -Path $Path

    # Save only needed individual rules.
    if ($KeepExisting.IsPresent) {
      if ($KeepDefault.IsPresent) {
        # Keep everything
        $acl.Access | ForEach-Object { $tempACL+=$_ }
      }
      else {
        # Remove the defaults, keep everything else
        for ($i=0; $i -lt $acl.Access.Count; $i++) { 
         if (!$aryDefaultACL.Contains($acl.Access[$i].IdentityReference.Value)) { $tempACL+=$acl.Access[$i] }
        }
      }
    }
    else {
      if ($KeepDefault.IsPresent) {
        # Keep only the default, drop everything else
        for ($i=0; $i -lt $acl.Access.Count; $i++) { 
         if ($aryDefaultACL.Contains($acl.Access[$i].IdentityReference.Value)) { $tempACL+=$acl.Access[$i] }
        }
      }
      #else { # Do nothing, because $TempACL is already empty. }
    }

    # Add the new rules
    # I could have been modifying $acl this whole time, but it turns out $tempACL=$acl doesn't work so well.
    # As the rules are removed from $acl, they are also removed from $tempACL
    for ($i=0; $i -lt $AccessRuleList.Count; $i++) { $tempACL+=$AccessRuleList[$i] }

    # This is the object that you're looking for...
    $aclDS=New-Object System.Security.AccessControl.DirectorySecurity -ArgumentList @($Path,[System.Security.AccessControl.AccessControlSections]::None)
    # The object, apparently, comes with a bonus rule...
    $aclDS.RemoveAccessRuleSpecific($aclDS.Access[0])
    # Add the rules to our new object
    for ($i=0; $i -lt $tempACL.Count; $i++) {
      # I tried adding the rules directly but they didn't work.  I have to re-create them.
      $tempRule=New-Object System.Security.AccessControl.FileSystemAccessRule -ArgumentList @($tempACL[$i].IdentityReference,$tempACL[$i].FileSystemRights,$tempACL[$i].InheritanceFlags,$tempACL[$i].PropagationFlags,$tempACL[$i].AccessControlType)
      $aclDS.AddAccessRule($tempRule)
    }
    # This has to be done after all the rules are added, otherwise it doesn't work
    $aclDS.SetAccessRuleProtection($true,$false)

    if ($ResetOwner.IsPresent) {
      # Often, the default owner is SYSTEM.  This ownership will prevent you from making any changes.
      # So, we change owner to the local Administrator
      $acl.SetOwner($owner)
      # We have to apply it now because we are applying our ACLs in two stages.  We won't be using Set-Acl again.
      Set-Acl -Path $Path -AclObject $acl
    }

    # Lastly, apply our ACls
    $dir=Get-Item -Path $Path
    $dir.SetAccessControl($aclDS)
  }
}