Per the board's policy, all policy changes must be announced in one board meeting, then voted on at a later board meeting. They cannot announce a change, and then immediately vote on it in the same meeting.
In order to get around that they are holding two board meetings tonight, one at 6pm to announce the change, and then one at 6:30pm - their normal meeting time - in order to vote on it.
The change appears to be in response to the large group of LGBT activists, many of whom came from outside the school district at the last board meeting. Ever since the district chose to read "I Am Jazz" to the entire elementary school population last December, and the resulting largest boycott ever in the school district (some classes were down to 5 students), the school board has been receiving questions and comments from both sides of the issue in every meeting.
The demonstrations have been growing in size and anger, and the board now seems to be taking significant measures without public notice or comment in order to control their meetings better.
Current policy: http://neola.com/saline-mi/ 0167.3
Special board meeting agenda (contains updated policy) (6pm): https://www.salineschools.org/downloads/_news_/20190611600_board_packet.pdf
Regular board meeting (6:30pm): https://www.salineschools.org/downloads/_news_/20190611_agendaandpacket_2.pdf
Further, it appears they are actually voting on the policy change in the first board meeting, thus violating their own policy of having policy changes announced in the board meeting prior to the meeting where it will be voted on. There is provision for an emergency policy change, but the meeting minutes don't suggest this is the process they will use.
Policy on policy change: http://neola.com/saline-mi/search/policies/po0130.htm 0131.1
Regardless, the sudden change, violating their policy on changing policy by not giving the public the usual two weeks between meetings to review and comment on the policy is extraordinarily troubling and speaks towards lack of transparency and difficulty in grasping a situation that is rapidly spinning out of their control.