Don't think that the introduction of quarantine was an opening for hacking educational institutions. Hacker attacks began long before the COVID-19 pandemic and the mass shift to online learning. A year ago, the school district in San Bernardino, California, became the target of ransomware attacks. According to Tessian, the University of Utah and the University of California paid ransom payments of $457,000 and $114,000 respectively to gain access to their systems.
Secondary education institutions (below the college level) are the most vulnerable to hacking. Cyberattacks on schools are cheap for criminals, but it can cost the schools themselves millions of dollars to prevent or recover from them. School districts simply do not have the resources, both financial and human, to handle such attacks.