Here is the central school staff. (As it refers to one unit.)
Yes
All staff are invited would be considered correct in English usage. American usage may be different.
Please list on of my staff to submit timesheet.
In this sentence, it would be clearer to say, "all staff use whole group instruction."
Please find attached the leave schedule of all staff for the holiday
All certified staff needs to complete a release of liability form.
you cellphone number aswell as number of others staff are included
staff are
no, that is definitely not proper grammar.
The staff was is correct
Yorktown Central School District's motto is 'Inspiring students, parents and staff to strive together for excellence'.
correct