The most common phrase is "nose to the grindstone," as in "He really has his nose to the grindstone this week."
An idiom that conveys the idea of studying hard is "burning the midnight oil." This phrase suggests staying up late working or studying, often implying dedication and effort. It captures the essence of putting in extra hours to achieve academic success.
working like a dog
Busting your balls is an idiom that means working very hard at something.
"Hit the books."
hard working
Life Is Sometimes Hard
No, if something is "like" something else, it is a simile.
It's not an idiom. "Fruits" means the end result of something, so "fruits of labor" would be what you earned from hard work.
Hard nosed
The idiom "a nut to crack" has the basic meaning of "a problem to solve." Some "nuts" are hard to "crack," while others are easy, but this can only be determined by context.
more hard-working, most hard-working
Pagsusunog ng kilay is a Filipino idiom that means working hard or burning the midnight oil in English. It refers to putting in a lot of effort and dedication to complete a task or achieve a goal.