My 10 year old son is perfectly capable of using loo roll to wipe his backside, so I consider he should also be expected to use a small wodge of loo roll to wipe down any excess detritus that he may leave spread down the side of the toilet bowl when he hasn't been bothered to sit on the seat straight. I don't expect him to start flinging chemicals round, or expect it to be perfectly spotless, but is it unreasonable for him to make some effort? His father thinks that it's unhygienic as he may not wash his hands properly, whereas I argue there is no more (potential) exposure to fecal matter than wiping his bum.