What's the best way for my son to get work tutoring maths for A level and GCSE students?

[LilacCadillac]

Just that really.
He's just finished A levels and got A in maths and A in further maths and is going to study maths in Uni
He's tutored a couple of kids a few times over the summer but would like to do more.
Is it mainly word of mouth and advertising his services on local Facebook groups?

My son does this. He works full time and is at uni and he got it through gumtree and charged a little less that what most do but also made sure people knew he was over qualified for what he was offering if you know what I mean by putting in what else he was doing in life… I think that made a big difference. He tutors 4 folk over a weekend… it’s not a full time job obviously as he has one but I definitely think painting a picture of where the tutor is at right now along with assuring people it’s not being treated like a side hustle is the way to go.