<p>Evanston Township High School is closed until at least Wednesday because of a cyberattack that occurred over the weekend, school officials announced. </p><p>A ransomware attack "disrupted access to district systems, internet services and computer infrastructure" and forced the school to cancel summer classes, sports camps and other on-campus activities that were scheduled, according to a note on the high school's website. </p><p>In a statement, the school said closing was necessary because it impacted systems critical to "safely" operating campus, such as network access, internet services, phone services, and other emergency or operational systems." The school closed Monday after the attack on Sunday.</p><p>ETHS said it didn't yet know when it would reopen, but would determine that within the next 24 hours based on "the progress of the investigation, system restoration, and confirmation that ETHS can safely resume operations."</p><p>"The district is working with cybersecurity forensic experts to determine what information, if any, may have been accessed or acquired," the school said in a statement to the Sun-Times.