If a student is found responsible and placed on probation at their college or university, their rights are going to depend, in part, on the particular school involved. Different schools have different policies in terms of what would be allowed at that point.
Most schools are going to have the right to an appeal. So if a student is found responsible and placed on probation, often they would have the right to appeal. The appeal bases are generally narrow in scope.
For example, was there a procedural error or defect which led to the outcome which led to the probation? Was there a new evidence that's now available that could provide, say, for a different outcome or potential sanction or, say, an argument that the sanction is disproportionate to the finding of responsibility? Will also depend on the nature of the offense itself. If it involves Title IX sexual misconduct, say, or an academic integrity or misconduct charge or, say, a general disciplinary issue such as, say, hazing. Schools also have the consideration that if an appeal right under Title IX is allowed to one party, it has to be allowed to both parties.
An experienced attorney adviser can help protect your rights, can let you know exactly what needs to be done to try to get a better outcome and should be involved throughout the process, but especially if a student is found responsible for some kind of misconduct and needs to appeal a finding or responsibility.