This is an interesting article. "Iwas sat/stood" really grates on me, but it is used more often than "sitting/standing" now - or so it seems when I listen to radio or TV. So maybe that is what the language is developing towards, so children should not be penalised for this as it is what they hear around them all the time. Ditto with "bored of" - it makes me gasp, but it is now common parlance.
Language does develop; and those things which made teachers very cross (which is why we gasp! - we are waiting for the ruler to fall!) when we were small are now the language of news readers and politicians and many people in the media.