Ok, after the last two levels, the Student's test has finished, which means after you respawn, the Box will stay in its own place! Moreover, you just need to push it three times to get all the way to the next level.
Unfortunately, the level is quite long, and you need to push all the way through it. Make use of her ability to flip upwards and maneuver through the level.
Keep it up! The next one is the last level of this minigame, the final compulsory part.