No it isn't. If a genuine leader thinks that standards of teaching and learning are not ok in some classes, then a discussion, where planning would be a part, with those teachers only is what is required. And individual discussion and the causes of problems explored and addressed is what will make a difference. Asking for everyone's planning will do nothing at all. Some people have lovely looking planning, but naff lessons. Others have naff looking planning, but excellent lessons. Sharing planning in an INSET means some people bring lovely planning that has no relation to normal practice and people will dreadful looking planning are pulled up even though they are excellent teachers. And what a total waste of time for all those staff who are planning and teaching fab lessons.