"Monopoly power" is not a monopoly and in the UK, public schools are actually private schools, so maybe we shouldn't compare terminology across countries.
"Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power"
That’s because competition/antitrust law, be it UK, EU or US, doesn’t care about whether an entity is a “monopoly” or not. It cares about whether a company is engaging in anticompetitive practices or not. The market share is a red herring.
Fortunately, "monopoly" isn't the thing that the law cares about.
Everything to do with anti-trust law, and competition laws, is not about monopolies, and is instead about monopoly power.
> so maybe we shouldn't compare terminology across countries
Feel free to look at the the FTC says about this topic then. It to applies to companies with monopoly power, and not literal monopolies.
https://www.ftc.gov/advice-guidance/competition-guidance/gui...
"Courts do not require a literal monopoly before applying rules for single firm conduct; that term is used as shorthand for a firm with significant and durable market power"