Technically, the majority opinion was 6-3. Thomas dissented entirely, claiming the search was legal. Two other judges said the search was illegal AND the administrators should be held liable for their actions. Six judges said both the search was illegal, but the administrators should NOT be liable.
Thomas also agreed in part. I haven't had the chance to read the whole thing but it seems he opposes the decision but supports the liability.
SOUTER, J., delivered the opinion of the Court, in which ROBERTS, C. J., and SCALIA, KENNEDY, BREYER, and ALITO, JJ., joined, and in which STEVENS and GINSBURG, JJ., joined as to Parts I–III. STEVENS, J., filed an opinion concurring in part and dissenting in part, in which GINSBURG, J., joined. GINSBURG, J., filed an opinion concurring in part and dissenting in part. THOMAS, J., filed an opinion concurring in the judgment in part and dissenting in part.