Depends partly on which ones u mean?
First 100? 200? 300?
Half of them are regular spellings (e.g. a, and, as, at, had, has, that, an, back, can, in, is, it, if ...) and will be learnt as part of basic phonics teaching.
The other half (e.g. I, he, of, the, to, was, first, her, off, they, new ...) clearly take longer to stick. It's good for children to know most of them by the end of Y2, because then they make fewer mistakes in their writing, but some children will continue to misspell quite a few of them for much longer.