The plural of activity is activities.
The plural of business is businesses.
The plural of bucket is buckets.
No, "school of fishes" is not the correct way to refer to a group of the same type of fish. The correct way to say that is "school of fish" since the plural of fish is fish.
The plural of pony is ponies.
As a title, it doesn't matter. In grammar, if you are talking about bringing music, you could say "music is on the way". In plural: same. You could also say "Your music is on the way" or "Her music is on the way".
That is the correct spelling of the plural noun "mushrooms."
He and i am going to school
The correct plural of the word "status" is "status." Although spelled the same way, the plural form is pronounced in such a way so that it rhymes with "loose."