What project types best prepare students for real-world software engineering?

I am leading a university coding lab where students work in teams on 3-month projects. The goal is to help them become job-ready junior developers by working on problems that reflect real-world engineering challenges.

I would like to avoid typical beginner projects and instead focus on systems that teach practical skills.

My question is: based on real industry experience, what types of projects or systems provide the most practical learning value for junior developers?

I’m especially interested in concrete suggestions or examples that could realistically be scoped into a 2–3 month team project.