A child may ride in a safety belt with a shoulder harness if the shoulder harness goes across the child's chest and not across the child's face or neck. The lap belt should fit low across the child's thighs or top of the legs and not across the child's stomach area. Never put a shoulder belt under the child's arm or behind the child's back. If the lap belt and shoulder harness do not fit properly, a booster seat must be used.
26 Tex. Admin. Code § 746.5615