RedKite said..
Never seen the sailing school staying in the 5 knots limits or staying within 50m of others (e.g people on a SUP).
Different rules for different people ?
Yes in fact there are different rules for different vessels on the water. Kiters and windsurfers are a vessel. Whether you like it or not.
But the general rule is, a vessel with better ability to manoeuvre must give way and space to the another vessel that has less ability to manoeuvre.