Our high school parking lot is set up very nicely for driver’s training, with somewhat narrow lanes marked out, a variety of parking scenarios, and a pair of figure 8 tracks that are tight for a car but fun at higher speed on a motorcycle.
You might find something similar at your local school.
I use the marked intersections for practicing swerves and sudden stops, and the figure eights to see if I can make my foot pegs shorter.
Your concerns over leaning are the easiest to address. Go pull figure eights in a parking lot, increasing speed until you can hear the foot pegs scrape. Just keep your feet tight against the bike and your knees against the tank. Wear full gear, including pants and heavy boots, so that if you misjudge things you won’t get any injury other than a bruised ego.