worried my 10 yr old son wont reach level 4 in year 6

[Ladyemem]

My son is at the end of year 5 and working at level 3b in his literacy. Last year he was 3c and the year before 2a. So each year has gone up one sub level. Should I be worried. I know I shouldn't compare but his younger sister is level 3a and only 8 and I can't understand why he struggles. (He isn't aware of this) we try and encourage him to read and help with his writing. anyone else in similar circumstances ?

I'm a y5 teacher.
Sounds like slow progress over the last 3 years, have school already talked to you about this?
It would be reasonable to expect a 4c for sats, however, given the history of slower progress i'd want to know what i could do to help - e.g. They will know which areas he needs to work on. If it's sentence structure (as it often is at this point) there are lots of grammar and writing books available in places like whsmith that you could have a go at over the summer.
I wouldn't worry but i would def talk to school and do something. Hth.

There will be a lot of boosting in Y6 which will get him to level 4 if he is capable of getting there.

If he doesn't then rejoice, it should trigger help at secondary. It is much better if he doesn't "just scrape" level 4's, as sometimes it triggers funding, and anyway provides evidence that he "needs help".

However what help has his school been giving him so far? what help are they going to give him next year?