class - form - grade - year
A class is a group of pupils or students who are taught together.
If classes were smaller, children would learn more.
I had forty students in my class.
In some British schools and in some American private schools, form is used instead of ‘class’. Form is used especially with a number to refer to a particular class or age group.
I teach the fifth form.
She's in Form 5.
In British English, a year is a set of students of a similar age, who started school at around the same time.
‘Which year are you in?’ – ‘I’m in the fifth year, and Krish is in the third year.'
A grade in an American school is similar to a form or a year in a British school.
A boy in the second grade won first prize.