Never assume today's less able child isn't forming ideas and plans.
DS1, who has ASD, was bottom of all his classes in primary, now at Comp level he is top of them.
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Why should the brightest children have to learn "patience" in being given work which is too easy? That's not differentiation' no, but it is life; very few people will find a job that is all challenge, especially without going through a few levels of boring filing first.
Did I feel guilty about the children who sat with the ds's whilst theyw re getting to grips? Well, did the parents feel guilty about my time when I sat with their kids listening to them read- it was ds's Sn that freed me from work to do that after all!
Of course it should only be sometimes and there will always be schools that get things wrong as in every other aspect of life...
Anyway my experience:
I was a bright child- reading early, top of year in English at primary and all that. I used to be paired with a child who had severe SN- we were an inclusive school even in the 1970's. Long term I can only be thankful; when my own children were born with a disability I lacked that feeling of being in another world that my husband had. We might not have to teach people less able than ourselves but we may well become the parent of one. We may become one ourselves. or we might be nursed by a less academic schoolmate in a care home, have them take care of our grandchildren.
Obviously balance is important but if you think you can write off a child in the early years you re wrong. if you think you can guarantee a life free from scenarios where empathy (which is developed by these experiences) or even direct experience of those with SN or LD is a survival skill, you are wrong.
Obviously if a child isn't get enough stimulation you need to talk to a teacher, and that is your job as parent just as much as it is my job to talk to them when my boys struggle.
Also ask why your child is paired; ours is a Church school in a naice village and chooses not the very brightest but the kindest and most compassionate. When ds2 (the NT one) is chosen I am so very proud of him.