(a) In each public school classroom, the teacher in charge may, or if so authorized or directed by the board of school directors by which he is employed, shall, at the opening of school upon every school day, conduct a brief period of silent prayer or meditation with the participation of all the pupils therein assembled.

(b) The silent prayer or meditation authorized by subsection (a) of this section is not intended to be, and shall not be conducted as, a religious service or exercise, but shall be considered as an opportunity for silent prayer or meditation on a religious theme by those who are so disposed, or a moment of silent reflection on the anticipated activities of the day.