The Taiqing and Shangqing schools of Taoism have distinct approaches to the concept of "shijie", which refers to the practice of self-cultivation and purification to achieve immortality.

The Taiqing school emphasizes living among terrestrial paradises rather than ascending to heavenly realms. This approach focuses on the cultivation of the self through practices that allow the practitioner to remain on earth and enjoy a long, peaceful life within these paradises.

On the other hand, the Shangqing school introduces meditation methods aimed at creating an immortal body. This path is more focused on ascension to the heavens and involves a deeper engagement with celestial beings and scriptures. The Shangqing practitioners aim to purify themselves to the extent that they can reside permanently in the Shangqing heavens.

In summary, the Taiqing school's approach to shijie is more earth-bound, seeking to live long lives within terrestrial paradises, while the Shangqing school seeks to ascend to the heavens through meditation and purification practices. For more detailed information, you can refer to the Wikipedia page on Shijie (Taoism) and the Stanford Encyclopedia of Philosophy's entry on Religious Daoism.