The threats involved Billy Baines Middle School in Missouri City and Harmony School in Katy.
"We take every threat seriously and will work quickly to ensure our community is safe," Sheriff Troy Nehls said in a statement.
The suspects -- 14 and 15 years old -- were arrested after an investigation.
According to officials, the 14-year-old student at Baines posted on Snapchat with the message "I'm going to shoot up the school." Another student saw the snap and told their parents, who called authorities.
Another photo was posted on social media threatening violence at Harmony.
Officials said the 15-year-old Harmony student posted an image of students fleeing Marjory Stoneman Douglas High School in Florida with the statement that something similar was going to happen to seventh graders at Harmony.
Nehls said the teen also posted a link of how to sneak guns into school.
"Parents need to have a conversation with their child about the seriousness of posting threats on social media," Nehls added.
Both teens have been charged with making a terroristic threat and were taken to the juvenile detention facility.