When teaching my two boys to piss in a toilet bowl I put a ping pong ball in it which resisted flushing down the hole . It gave them a target to aim at. Worked a treat. Maybe you can try that. Personally my aim is fine
Discussion
I slightly bend the knees if I feel I don't want to sit on one (public etc) but most toilets over here splash if you piss in them standing straight. I blame the modern design.