School computers are notoriously underpowered. Modern Minecraft (1.19+) requires at least 4GB of RAM and a decent GPU. Version 1.5.2 can run on 512MB of RAM with integrated graphics from 2010.
: Minecraft 1.5.2 was the last version to support older Java versions (Java 5/6) and PowerPC Macs, making it highly compatible with legacy systems. Unblocked Minecraft 1.5.2
A: Possibly. If you download a massive .exe file from a suspicious site, their antivirus will flag it. The safest method is Eaglercraft (it looks like a generic HTML5 game) or using an offline launcher from a USB stick that never touches the internal hard drive. School computers are notoriously underpowered