My son's school introduced 100 word spelling tests a few years ago. These are carried out in one sitting from Y3 onwards. In order to move onto the second list of 100 they have to score 95. DS is now in Y5 and is still on the first 100. Going back through his tests from Y4, he has had between 90 and 94 correct each time, with different words incorrect. These words are: to/too, one/won, their/they're, its/it's, sometimes other words.
DS tells me that the teachers don't always make it clear (i.e. put into a sentence) that they want "to" not "too" etc.
I teach clarinet and can't imagine holding a child back from grade 2 because they didn't get a distinction in grade 1, but this is what the school are doing IMO.
Now, at his age I would (and still am) have been horrified to get any words incorrect and would make sure that I didn't make the same mistake again. But that was me and I'm a perfectionist (it takes me forever to write a post).
Do any of you have the same spelling test system in your DCs schools and, if your child is being held back because of silly a few, easily confused words, would you approach the teacher and tell them that you think it is unreasonable to keep a child on the same list for 3 years.