Believe it or not, both are correct. It's a special group of words: family police staff etc They can take either the singular or the plural.

I would echo others here: both are acceptable, it depends on the use. As a rule of thumb, if the word can be prefaced by "members of" (i.e. "members of staff", the multiple individuals that make up the collective), then I think it sounds more natural to use "are". - (Members of) staff are expected to arrive at work on time. - The staff is made up of 20 full-time employees.

Usually it sounds more natural to use "staff is" because in most cases, the staff is considered as a unit. Even though it contains a number of people, it is usually taken as a singular entity. ................................ Similar examples are not hard to find : 1) The school STAFF IS made up of 30 members. 2) The basket of eggs IS broken. 3) Our team IS the best team................................ Also, depending on the context, there might be instances where you may be referring to the entities in the group. In those cases, "staff are" would be more appropriate. e.g. 1) Members of the school STAFF ARE experienced people. 2) The eggs in the basket ARE broken 3) The players of our team ARE very good sportsmen......................... Also, take this small test to test your understanding of singular and plural http://www.better-english.com/grammar/sinplu.htm

based on the situation we are using both is & are

It is a collective noun. The staff probably consists of more than one person, but the word "staff" is countable. Therefore, singular is called for.