Telling tales out of school means divulging secrets or confidential information. There are several other phrases that convey the same meaning. One such phrase is talking behind someone's back. This means speaking about someone behind their back, often saying negative things about them. Another phrase is blabbing, which means revealing secrets or information that was meant to be kept confidential. Spilling the beans is another popular phrase that suggests revealing secret information. Gossiping is also a common synonym for telling tales out of school. Lastly, divulging secrets or sensitive information is often referred to as ratting someone out or snitching. All of these phrases should be used with caution as they can cause hurt feelings and damage relationships.