Slader can be a helpful resource for students. Slader promotes itself as providing textbook solutions written by subject matter experts. It sounds good in theory. The unfortunate reality of it is though that depending on the circumstance, the student can definitely find him or herself charged with an academic misconduct, a violation for using Slader.
Whether or not it's appropriate to the circumstances or the student was in within his or her rights to do so would depend on the facts of the case, the circumstances involved, in other words. Did the professor of the school specifically prohibit a student from using an outside resource or an online resource such as Slader? If the answer of that is yes, then it very well could be or would be an issue. If the school was less clear in that regard, then, again, the student may not be culpable for any wrongdoing.
The specific circumstances at hand need to be carefully considered. You cannot depend on the school to do the right thing. Before you engage with the school in any capacity, you do need to take the necessary precautions. Having an experienced attorney advisor will be your best ally to help you understand and navigate the process.