The Highest I have ever jumped was many years ago when I was in College and that was 5'5. Now that because the horse looked after me as I was at the limit of my experience.. Jumped it twice and after that couple of years later started competing at average 4'5.. Now well I haven't been jumping for 5 years so I guess 3 or 3'5 with confidence.
Before my 16 yr old TB was injured and retired, we got up to a little over 3'. Now I have a 3 year old that won't be jumping for a while, but I hope to (and plan to, permitting he is able/comfortable with it) go higher. My goal is at least 4'. :)