Microsoft project management software used to plan, manage, and communicate a project schedule and other information among workgroup members, project managers, and other stakeholders.
Your question is a bit vague, so it will be hard to give a specific answer.
First, it might be due to licensing issues. Project is not part of the free licenses Microsoft offers to the school - For example Office 365 Education suite (Word, Excel, PowerPoint, OneNote). It usually requires a separate license. So either you or your school needs to subscribe to a paid license from Microsoft to have access to it.
Second, assuming you have the necessary license, there may be technical issues that may prevent it from downloading, like internet, logging in using the right credentials..etc.
Best check with your school IT admin on this.