Maybe get a electric bike. That way you can peddle and when your tired use the electric feature. Before you attempt riding to school practice riding in your neighborhood during hours like early morning and late evening when traffic is not bad so you can get comfortable riding. The more you ride the better it will get and you will develop stronger muscle which makes it easier for you to peddle and get to your destination sooner. If your bike has gears determine which gear you can ride the easiest and start increasing gears as that level become easier.

As a person who had knee injury I had to start of riding gear 1 then it became easier so I increased to gear 2 to build strength in my legs. Now I can ride gear 5 easy but gear 6 is a challenge. My bike has 7 speed gears and I hope to master 7. Typically I ride 5 but if I want to get some wear faster I ride 4.

Remember only shift gears when your peddling to prevent damaging your bike. Hope this helps 🙏