SINGULAR OR PLURAL FOR GROUP OF PEOPLE

Which phrase is correct - the class was or the class were? Is the word class a singular noun or a plural noun? This question cannot be answered with Yes or No. Use the singular if you see the class as a group of students. Use the plural if you see the class as single students.
In British English the plural is used more often than in American English.

sentence	explanation
The family is on holiday.	I see the family as a group.
The family are packing their suitcases.	I see the single members of the family packing their suitcases.

sentence	explanation
Team B was very successful today.	I see Team B as a group.
Team B were very successful today.	I see the single members of Team B. Each member of the team was successful. I could also say: All members of Team B were very successful.

There are more words which can be singular or plural nouns:
army, band, choir, class, club, crew, company, firm, gang, government, orchestra, party, staff