(a) For the purposes of Texas Education Code, §21.405, a school district shall use the guidelines in this section to determine what constitutes a personnel shortage, extreme economic conditions, or an unavoidable or unforeseen circumstance.(b) A personnel shortage exists when, despite reasonable efforts of a school district to use nonteaching personnel or the assistance of community volunteers to supervise students during lunch, there are no other personnel available.(c) Extreme economic conditions exist when the percentage of a local tax increase, including any amounts necessary to implement this section, would place the district in jeopardy with respect to a potential tax roll-back election as provided in the Texas Property Tax Code, §26.08.(d) Unavoidable or unforeseen circumstances exist when, due to illness, epidemic, or natural or man-made disaster, a school district is unable to find an individual to supervise students during lunch.