This bus is on a circular route between the school and the station, and you can freely get on or off anywhere along that route!
I recommend it; it's super convenient!
「このバスは駅と学校の間を循環してて乗り降り自由！」は英語で「This bus circles between the station and the school, and you can get on and off freely！」という表現が良いと思います。
循環するーTo circulate・To cycle・To rotate・To loop
循環バスーLoop-line bus・Loop bus・Bus on a circular route
乗り降りーBoarding and alighting・Getting on and off （Ａ bus）
This bus circulates between the station and the school, and you can hop on and off freely!
*This bus circulates between the station and the school, and you can hop on and off freely!*
*It's a loop bus that runs around the area and lets you get on and off anywhere along the route.*
**乗り降り自由**という表現には、“hop on and off freely” や “get on and off anywhere along the route” が適しています。
- “hop on” / “hop off” はカジュアルな乗車・下車の表現で、特に観光バスやシャトルバスに多用されます。
アメリカ合衆国 
