Tex. Education Code § 25.112

(a) Except as otherwise authorized by this section, a school district may not enroll more than 22 students in a prekindergarten, kindergarten, first, second, third, or fourth grade class. That limitation does not apply during:

(1) any 12-week period of the school year selected by the district, in the case of a district whose average daily attendance is adjusted under Section 48.005(c); or

(2) the last 12 weeks of any school year in the case of any other district.

(b) Not later than the 30th day after the first day of the 12-week period for which a district whose average daily attendance is adjusted under Section 48.005(c) is claiming an exemption under Subsection (a), the district shall notify the commissioner in writing that the district is claiming an exemption for the period stated in the notice.

(c) In determining the number of students to enroll in any class, a school district shall consider the subject to be taught, the teaching methodology to be used, and any need for individual instruction.

(d) On application of a school district, the commissioner may except the district from the limit in Subsection (a) if the commissioner finds the limit works an undue hardship on the district. An exception expires at the end of the school year for which it is granted.

(e) A school district seeking an exception under Subsection (d) shall notify the commissioner and apply for the exception not later than the later of:

(1) October 1; or

(2) the 30th day after the first school day the district exceeds the limit in Subsection (a).

(f) If a school district repeatedly fails to comply with this section, the commissioner may take any appropriate action authorized to be taken by the commissioner under Section 39.131.