The seat was vacated last month by Wanda Adams, who resigned following her election as a justice of the peace.
Guidry has operated a private practice focusing on family and probate law for the past two decades.
She will fulfill Adams' term which ends on Dec. 31, 2021.
The appointment comes before the HISD District Board of Education is scheduled to meet Thursday at 5 p.m.
The #HISD Board of Education voted unanimously this evening during a special meeting to appoint Myrna Lynn Guidry to the District IX seat vacated by Wanda Adams. The Board will swear in Guidry at noon on Thursday before its regular meeting.— Houston ISD (@HoustonISD) December 9, 2020
The board is scheduled to accept a $250,000 grant from school-based Healthcare Solutions Network to address students' and parents' mental health issues caused by the COVID-19 pandemic.
The grant will be used at 10 participating schools to assist families whose students are enrolled in virtual or face-to-face instruction.
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The following schools will receive the grant: Highland Heights and Wesley elementary schools; Attucks, Cullen, Henry, and Thomas middle schools; and Bellaire, Madison, North Forest, and Waltrip high schools.
Also at Thursday's meeting, the board is set to approve an agreement for the University of Houston to hire, train and supervise select students to tutor and mentor HISD students enrolled in the district's Miles Ahead Scholars (MAS) program, as well as targeted students who attend Kashmere, Wheatley and Worthing high schools.
The UH students would work with a teacher at the high schools or a program manager with the MAS program. UH tutors would also provide MAS students with college application guidance.
The board is also scheduled to vote on the district's annual targeted improvement plans for comprehensive support schools that require additional resources, and for schools that received an F rating from the Texas Education Agency (TEA) during the 2018-2019 school year.
Additionally, the board is set to accept a $20,000 donation from the family of the late Irma Rodriguez, who was a veteran teacher at Sanchez Elementary School.
The donation would be used for instructional classroom technology.
SEE ALSO: Houston teachers' union asking for all schools to go virtual
Rodriguez is remembered as a devoted, award-winning, generous teacher who donated toys, laptops, and groceries to assist students and their families.
Trustees are also scheduled to vote on a $20,000 cash donation from the Houston Texans and Reliant and NRG company, for eight HISD schools to support technology.
The Texans and Reliant are also donating $84,000 worth of drawstring bags, phone chargers, and Deshaun Watson jerseys and autographed footballs to reward attendance.
Also, the board will consider $10,000 worth of supplies and materials donated by FedEX's Purple Totes campaign to four HISD elementary schools in response to wish lists provided by the schools.
Trustees will also consider a $31,700 in-kind donation of video production equipment and a sound mixing console from NASA's Johnson Space Center for Sam Houston Math, Science, and Technology Center High School to support STEM education through student-led productions.