There's no universal rule
Disclosure rules, spent-conviction laws and employer policies are different in every country and every school, and they change. A caution from a decade ago might be irrelevant in one country and disqualifying in another. Nobody — including us — can tell you 'you're fine' without seeing the actual visa requirements for the country you want and the specific offence on your record.
What we can say is that the honest route is almost always better than the hopeful one. Applying without disclosing, and hoping the background check doesn't surface an old offence, tends to end with a cancelled visa, a lost flight, and no refund from the school.
