Here is the Florida language / statute regarding retired school bus usage.
It only talks about paint and markings, not lights.
https://www.flsenate.gov/Laws/Statutes/2018/0316.72
316.72 Buses simulating school buses in color and insignia; conditions of use.—
(1)
It shall be unlawful for any person, except a governmental unit or agency operating as provided by law,
to use on the public highways of the state any bus of an orange or yellow color known as “school bus chrome,” or any color purporting to resemble the color of a school bus, for any purpose other than to transport persons to and from educational or recreational facilities or institutions or to and from events or activities which are sponsored, financed, or supervised by educational, recreational, religious, or charitable organizations. When said vehicle has ceased to be so used, or is used for the transportation of passengers other than for said purpose, its use shall be unlawful unless and until said bus has been changed from said colors to some other color by repainting and unless and until all signs and insignia which mark or designate it as a school bus have been removed therefrom. However, in school districts contracting for buses from an outside source or in school districts operating specially designed or equipped buses for the transporting of the handicapped, those buses may be used on a temporary or irregular basis to transport persons to and from facilities or activities not specified in this subsection within the county with the express consent of the school board.
(2) Any educational, recreational, religious, or charitable organization may own, operate, rent, or lease any bus which has been painted the orange or yellow color known as “school bus chrome” and which has been equipped with the signs, lights, insignia, and other features which normally characterize a school bus, as defined in s.
1006.25, consistent with the provisions of this section.
(3) Any person violating any provision hereof shall be deemed guilty of a misdemeanor.
(4) Any county or municipal ordinance contrary to the provisions of this section is hereby repealed.
History.—ss. 1, 2, 3, ch. 57-280; s. 5, ch. 61-459; s. 96, ch. 65-239; s. 106, ch. 72-106; s. 13, ch. 75-284; s. 2, ch. 78-104; s. 1, ch. 80-265; s. 40, ch. 97-190; s. 961, ch. 2002-387.
Note.—Former s. 234.041.
Florida - legal definition of a school bus...
https://www.flsenate.gov/Laws/Statutes/2018/1006.25
1006.25 School buses.—School buses shall be defined and meet specifications as follows:
(1) DEFINITION.—For the purpose of this part, a “school bus” is a motor vehicle regularly used for the transportation of prekindergarten disability program and kindergarten through grade 12 students of the public schools to and from school or to and from school activities, and owned, operated, rented, contracted, or leased by any district school board, except
a) Passenger cars, multipurpose passenger vehicles, and trucks as defined in 49 C.F.R. part 571.
(b) Motor vehicles subject to, and meeting all requirements of, the United States Department of Transportation, Federal Motor Carrier Safety Regulations under Title 49, Code of Federal Regulations and operated by carriers operating under the jurisdiction of these regulations but not used exclusively for the transportation of public school students.
(2) SPECIFICATIONS.—Each school bus as defined in 49 C.F.R. part 571 and subsection (1) that is rented, leased, purchased, or contracted for must meet the applicable federal motor vehicle safety standards and other specifications as prescribed by rules of the State Board of Education.
(3) STANDARDS FOR LEASED VEHICLES.—A motor vehicle owned and operated by a county or municipal transit authority that is leased by the district school board for transportation of public school students must meet such standards as the State Board of Education establishes by rule. A school bus authorized by a district school board to carry passengers other than school students must have the words “School Bus” and any other signs and insignia that mark or designate it as a school bus covered, removed, or otherwise concealed while such passengers are being transported.
(4) OCCUPANT PROTECTION SYSTEMS.—Students may be transported only in designated seating positions, except as provided in s.
1006.22(12), and must use the occupant crash protection system provided by the manufacturer, which system must comply with the requirements of 49 C.F.R. part 571 or with specifications of the State Board of Education.
History.—s. 299, ch. 2002-387.