Tex. Fam. Code § 51.09
Unless a contrary intent clearly appears elsewhere in this title, any right granted to a child by this title or by the constitution or laws of this state or the United States may be waived in proceedings under this title if:
Acts 1973, 63rd Leg., p. 1460, ch. 544, Sec. 1, eff. Sept. 1, 1973.
Amended by Acts 1975, 64th Leg., p. 2154, ch. 693, Sec. 9, eff. Sept. 1, 1975;
Acts 1989, 71st Leg., ch. 84, Sec. 1, eff. Sept. 1, 1989;
Acts 1991, 72nd Leg., ch. 64, Sec. 1, eff. Sept. 1, 1991;
Acts 1991, 72nd Leg., ch. 429, Sec. 1, eff. Sept. 1, 1991;
Acts 1991, 72nd Leg., ch. 557, Sec. 1, eff. Sept. 1, 1991;
Acts 1991, 72nd Leg., ch. 593, Sec. 1, eff. Aug. 26, 1991;
Acts 1995, 74th Leg., ch. 262, Sec. 8, 9, eff. Jan. 1, 1996;
Acts 1997, 75th Leg., ch. 1086, Sec. 4, eff. Sept. 1, 1997.