workhorse
A very reliable person or thing that does lots of hard work.
A workhorse is someone or something that does a large amount of hard, steady work without complaining or breaking down. The word comes from the reliable farm horses that pulled plows and wagons day after day, never the fastest or flashiest animals but always dependable when there was work to be done.
In a classroom, the workhorse might be the student who consistently completes every assignment thoroughly, helps classmates, and keeps group projects moving forward. On a baseball team, it's often the pitcher who takes the mound game after game, inning after inning. In an office, it's the employee who handles the essential tasks that keep everything running smoothly.
The word often describes things too. A workhorse laptop is one that runs reliably for years, handling schoolwork, research, and projects without fancy features or frequent failures. A workhorse car keeps running long after flashier models have broken down.
Being called a workhorse is genuine praise. It means people count on you because you're consistent, capable, and willing to do what needs doing.