If I have a student subscription to Apple Music do I get a free subscription to Apple TV ?

Yes, you get the same access as subscribers “for a limited time.” (That probably means that Apple reserves the right to make changes to this arrangement at some as-yet-undefined moment in the future.)

Get an Apple Music student subscription - Apple Support

“How to get Apple TV+

If you have an Apple Music student subscription, you can enjoy free access to Apple TV+ for a limited time. Just open the Apple TV app and start watching Apple Originals. You can't share your free Apple TV+ access with Family Sharing. Apple TV+ isn't available in all countries and regions.”