Question: I would love to send a Unix command through ARD that will change a OS X admin user to a standard user. The only thing I found close is 

```
sudo dscl . -delete /Groups/admin GroupMembership USERNAME

```

which does remove the user from the list of admins, but they are still listed as an admin in the user preference panel, and can still use their account to authenticate for admin privileges.

Answer: 
Just fought this battle, you can drop the `dscl` line and use the following;

Type the command :

```
sudo dseditgroup -o edit -d UserName -t user admin 

```

Where `UserName` is their actual AD username. 

Berry
I have done the below command, it is working fine

```
sudo dseditgroup -o edit -d UserName -t user admin 

```