How do I remove a person from a group text?

It is only possible to leave or remove people from a group conversation if they are using iMessages. Normal SMS messages (the Green Bubbles) cannot be removed, as they do not "run" under the same system as iMessages.

• iMessages are sent via data, through Apple.

• Normal SMS/MMS are sent via the "old fashioned network", via your Carrier.

You can read more about group messages here:

Send a group text message on your iPhone or iPad - Apple Support

You can only do that if everyone in the group is using iMessage:

Add and remove people in group text messages on your iPhone or iPad - Apple Support