Talk

Whilst they are at the match / tournament / event then they are the teacher's responsibility, but obviously whilst travelling in a car the teacher isn't in, then they aren't.
It's made clear (on the very rare occasions it's needed) to the dc they are representing the school, that so and so's Mum/Dad/Gran is kindly giving up time to enable them to get there, etc.,etc., and it's never really an issue about anyone playing up or not acting responsibly.
Not clear what you mean about normal staff ratios - What team has more dc in in than a class?

Thanks for your reply. By ratio's, what I mean is that on a normal trip or visit we adhere to a 1:10 adult:child ratio. At a sporting event outside school hours, then normally only one teacher attends regardless of how many children are there. Granted, it's usually less than 10 but not always.

But they will also have other adult support though - in the parents that drive them there. Surely the same as you would have if you took dc on a trip - you don't magic more teacher out of the air, you rope in volunteers.
That said, Primary schools are supposed to play in 'little leagues' and not play 'full sized' teams so, again, it seems unlikely they would be more than 10 anyway.

We have a similar system, parents are asked to take their child to an after school event and arrangements are made between those that can/can't. A teacher always attends but just the one, parents there are viewed as responsible for their child and the teacher responsible for the rest!

Spaniel - do you assist in sorting out those who can't get a lift and matching them up with those who can drive, or do you leave all that to the parents?

We have parents who regularly offer, others we just ask if they can! ( We are a small school so that probably makes it easier!)

Like Spaniel - it is theoretically for parents to sort out lifts among themselves, but there realistically has to be a certain amount of facilitating by the school if your goalkeeper's Mum doesn't know the Centre forwards Mum, or your flutist's Dad doesn't know the trombonist's Dad. However, that's all to do with liability over travelling in cars - if it's arranged by the school, then it's their responsibility whereas if 3 or 4 parents offer other dc lifts, then that's a private arrangement amongst parents, covered by their usual SDP insurance. It doesn't affect the number of children the teacher is responsible for at the match / concert / gala / display though.