Nationals of Australia, Canada, Japan, New Zealand, Singapore, South Korea and the United States of America are eligible to use e-gates at the airports when travelling to the UK as a visitor (standard) within the Immigration Rules or with entry clearance. These nationals must not use an e-gate if they wish to study in the UK as a short-term student for less than 6 months, unless they have obtained prior entry clearance.
Institutions will advise students of these nationalities that they need to see a Border Force officer to obtain an STS stamp on entry to the UK. This is in line with all of the advice on gov.uk and in ports of entry. This means that these nationals might be asked to leave the UK and come back for their passports to be stamped by a Border Force Officer to be allowed to study for more than 30 days.