Yes
All staff are invited would be considered correct in English usage. American usage may be different.
Here is the central school staff. (As it refers to one unit.)
Please list on of my staff to submit timesheet.
No, the correct term is "staff of laborers." The phrase refers to a group of workers who are employed for manual labor tasks.
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
Two senior staff members were granted scholarships.
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