The survey is compelling students, under color of legal authority, to confess to crimes. This confession can later be construed as "discoverable evidence" leading to actionable charges.
The objection here is to "fishing expeditions" wherein evidence is gathered en masse under an innocent pretext, and later (whether planned or not) an authority could gain access to that information and use it against the coerced students. Example: survey occurs, police find evidence of drug crimes with tenuous connection to a particular student, survey results are demanded via warrant by police, confession by student in question is revealed and a whole lotta other students' confessions are found and subsequently acted on.
That the evidence was elicited prior to development of a criminal case does not excuse compelling students to confess, whoever to, to otherwise unidentified crimes. If the evidence exists at the onset of criminal investigation, it cannot be recalled by the suspect under 5th Amendment grounds. That the confession is elicited by the state, to wit the public school, compounds the issue: the government is not allowed to demand evidence of criminal culpability without warranted cause, which is exactly what the school in question was doing.
Your statement of the rule is both too broad ("the government is not allowed to demand evidence of criminal culpability") and yet insufficiently broad to capture the activity the school engaged in (a survey by the school administration designed to gather information about potential psychological issues).
You missed the clause "without warranted cause" (make that "warrantable") in that quotation.
Broad-based gathering of information about potential psychological issues, without anonymity and with viable consequences of expulsion or prosecution, is nothing more than a "fishing expedition"/"witch hunt" - exactly the kind of thing the 4th and 5th Amendments are intended to protect against.
The objection here is to "fishing expeditions" wherein evidence is gathered en masse under an innocent pretext, and later (whether planned or not) an authority could gain access to that information and use it against the coerced students. Example: survey occurs, police find evidence of drug crimes with tenuous connection to a particular student, survey results are demanded via warrant by police, confession by student in question is revealed and a whole lotta other students' confessions are found and subsequently acted on.
That the evidence was elicited prior to development of a criminal case does not excuse compelling students to confess, whoever to, to otherwise unidentified crimes. If the evidence exists at the onset of criminal investigation, it cannot be recalled by the suspect under 5th Amendment grounds. That the confession is elicited by the state, to wit the public school, compounds the issue: the government is not allowed to demand evidence of criminal culpability without warranted cause, which is exactly what the school in question was doing.