Yes, it is legal to publish past work that you have created and similarly it is also acceptable to study from other students' past work. Similar to the use of academic journal articles published by doctorate students and exemplar responses provided to students by the university, students use Thinkswap resources to study from and develop on knowledge.
We recommend you familiarise yourself with your institutions's relevant 'Academic Integrity' and 'Intellectual Property' policies however, in general, you are considered to have copyright ownership of any work you create at university. Accordingly, unless you transfer copyright to another party, you own and are entitled to publish work such as past assessment tasks and study notes on Thinkswap.
Thinkswap makes clear that misuse of the platform is never acceptable and dealt with accordingly. Misuse includes but is not limited to: copying content from any one of our study resources and submitting it as one's own work and uploading another person's materials to Thinkswap without their permission (this includes any copyrighted materials not authored by the uploader).
For more information on academic integrity, please refer to our article 'Thinkswap and academic integrity'