Are they Working with Children (WWC) Approved?
In Western Australia, there is a compulsory screening strategy/test to check and protect all children from undesirable adults (people who have been convicted because of their relationship with children) banning them from teaching innocent and vulnerable children.
Don’t risk the safety of your children, instead, ask the Karate Club whether they’re WWC Certified and ask to view their registration card before joining.
Don’t live in WA? Check your state or country governing body for something similar.