Here are the steps on how to get a YouTube Music Premium student plan without YouTube Premium:

Go to the YouTube Music website or app.
Click on the "Get Premium" button.
Select the "Student" plan.
Follow the instructions to verify your student status.
Select your payment method.
Click on the "Buy" button.

Once you have completed these steps, you will be able to enjoy all of the benefits of YouTube Music Premium, including ad-free listening, background playback, and offline downloads. Please note that you can only have one YouTube Music Premium student plan at a time. If you already have a YouTube Premium subscription, you will need to cancel it before you can sign up for the student plan. Here are some additional things to keep in mind:

The YouTube Music Premium student plan is available in select countries only.
The student plan is a discounted rate, but it is still a monthly subscription.
You will need to verify your student status every year.
If you are no longer a student, you will need to cancel your subscription or upgrade to the regular YouTube Music Premium plan.

I hope this helps!