There are a lot of things that make a board game fun.
The first thing, and to me, one of the most important things is repeated playability. People want to get a good gaming experience everytime they play, but they don't want to play the same game every time either. This is why games come with so many variables (different spaces to land on, so many cards with different sayings on them, dice that can give you multiple outcomes, etc). If a game plays the exact same, with nothing new, people will become bored after the first game and will not be willing to play the game again.
Another thing that makes a board game fun is a fun concept. Pick a concept that people are interested in. If it's for a school project, then the subject, like statistics or geometry might not seem like fun to people who are not forced to play the game, so it's up to you to find a way to make the game fun. Using movers that are different shapes, sizes, colors, or characters can help motivate people to want to play to be their favorite piece or color, using a board full of fun graphics can help entice people to keep playing, and a good concept will keep people coming back to your game time and time again.