Clark says she didn't mean for everyone to see her thoughts and requests on immigration. She says she believed the tweets were private between her and the president.
But the very public messages have now embroiled her school district in scandal - and they could get her fired.
"Ms. Clark stated she did not realise the tweets were public," a Fort Worth Independent School District review said in a copy obtained by The Washington Post. Clark acknowledged the tweets were hers, the review said.
A district board meeting Tuesday will determine whether Clark will be fired after public comment, district spokesman Clint Bond said.
The inquiry substantiated "inappropriate behaviour" in violation of district regulations. Clark was placed on administrative leave with pay on May 29, two days before the last day of school, Bond said.
Her attorney Brandon Brim declined to comment ahead of the board meeting.
Clark's tweets angered parents and others, prompting a response from district superintendent Kent Scribner.
"Let me reiterate our commitment that every child in the District is welcome and is to be treated with dignity and respect," Scribner wrote May 29 on Facebook.
The response was so strong that the district urged parents and guardians to refrain from harsh language in a later post.
"I'm very surprised and concerned that this cruel woman has been berating our precious children for years," a woman wrote in response to Scribner. "Where was FWISD???"
The Supreme Court ruled in Plyler v. Doe that public schools are required to provide schooling for children, regardless of their immigration status. Schools cannot ask students about their immigration status or report them or family members to federal immigration authorities.
Clark, an English teacher at Carter-Riverside High School, has worked with the district since 1998, the review said, and has a history of violations - including insulting her students' ethnicity. Even before the tweets came to light, the district was already investigating separate allegations of derogatory remarks from Clark in the classroom.
Last month, when one student asked to go to the bathroom, Clark told the student to "show me your papers that are saying you are legal," a student told investigators, which was corroborated by another student.
She denied to investigators that she made the comment, which the report claims occurred May 17 - the same day Clark tweeted at Trump multiple times about what she perceived as illegal immigration in Fort Worth and in the school district.
Fort Worth's population is about a third Hispanic, according to city data.
In 2007, Clark kicked a student, the review said, though an investigation determined it was "without malice." In 2013, she was disciplined for referring to a group of students as "little Mexico" and called another student "white bread." Those allegations proved to be true, according to the review.
Clark's former Twitter account was filled with invective salvos directed to Trump in January and May, according to the report.
"Do you have someone who has looked at the crime statistics across our great nation and documented the number of time an illegal immigrant has committed an act of robbery or murder on American citizens?" she wrote to Trump.
The president has inaccurately linked violence to unlawful immigrants, who commit crimes at lower rates than US-born Americans.
But Clark assured Trump that her concerns were legitimate, the tweets show, and on May 17, she left her cellphone number for the White House to call.
"Georgia Clark is my real name," she wrote.
