Private schools - do any of them allow a relaxation of the dress code in summer?

Yes, a loosened tie is scruffy.

At the school I work in, 'summer dress' is no tights for girls, shirt sleeves neatly rolled up, no blazer but tie and top button to remain on and done up. In reality most ties/top buttons are loosened in lesson time and tightened up again before leaving the room.

Yes, shirt sleeve order was announced on a daily basis at my ridiculous school.

Yes

I've got no problems with "shirt sleeve order" I think its sensible. Its not being allowed to remove blazers, tie, jumpers, tail coats, etc despite the fact thats its a beautiful sunny day that I find completely incomprehensible.

Probably I dont think Henley Regatta is moving with the times. I belive skirts still have to be knee level or below. My DH also nearly roasted alive in his thick rowing blazer and boat club tie!

Is that still the case at Henley, do you know? I remember DH suffering in a heavy blazer (the only one he owned) on a sweltering day at Henley decades years ago.

Ok I've looked up the term "shirt sleeve order" as oshgosh says it is a military one and it means that you have been given permission by your CO to remove your tie/jacket etc undo your top button and role up your sleeves as already said there is no half way house.
At one stage it was just "not the done thing" to remove your jacket and leave your tie on or an even bigger sin remove you tie and leave your jacket on! Years ago when we were at Henley in the scorching sun men were told off for removing their jackets and ladies their stockings/tights.

We had hideous summer dresses when I was at (fee paying) senior school so were comfortable and smug compared to the boys at the school next door.

DC's prep school don't wear ties anyway, except on special occasions, so are normally to be found in chinos and short sleeved shirts (boys) and summer dresses (girls) in summer - far more representative of the real world, IMHO. They all moan like hell when some occasion demands that they spend all day in their "suits" (tweed jackets with shirt and tie, grey trousers for boys, kilts for girls)

Surely it would be either full uniform, or planters; not some weird hybrid?

Ds's school has a summer uniform. Which is lighter weight shorts, and a summer shirt with no tie plus short socks. They can wear their jumper if cold. No other mixing and matching though.

Even our state primary school insists on ties for the boys, although they can have short sleeves and no jumper. Not really a problem.

I was also very interested to note that my OH has been going to work (Inhouse lawyer in company on edge of City) without a tie. He says that ties are just not the done thing now...

I don't know about senior school but my DC's prep school lets them take their ties off and undo their top buttons in this weather.

They have to go into school in blazers and wear it when coming out at the end of the day but the minute they're out of the playground it's off.

At DSs school the boys always have to wear blazer and tie except when the school officially declares 'shirt sleeve order' but even then boys are only allowed to take blazer and tie off if they are wearing a white short sleeved shirt with the school logo on the pocket.

Girls have a light summer dress they are allowed to wear in summer term and first half of autumn term.

our school has a summer uniform. Younger girls swap kilts for summer dresses (with jumpers if they are cold) older girls swap to short sleeve blouses with their kilts. Boys can wear shorts and short sleeve shirts, on extremely hot days the headmaster will give them permission to remove ties, this is done in assembly so all the boys know.

I would share your concerns if mine DC?s were expected to wear completely inappropriate clothes in hot weather. No one can be expected to work effectively if they are over heating because its 85 degrees outside and you sitting in a jumper and blazer.
mummytime I?m interested by you schools uniform code. I?ve always been lead to understand that if you remove your jacket you always remove your tie, roll up your sleeves and undo your top button but maybe I?m more old fashioned than I like to think I am!
I understand (but I might be wrong as it?s a boarding school and ultimately I completely clueless about the day to day running of the school) that the boys at my DS?s school are told that its ?short sleeve order? and that they stay in this until instructed otherwise. To be told on a daily basis what you can wear also seems completely ridiculous.

DCs school has said "if you don't like the uniform rules go elsewhere", it is an oversubscribed Comp. They have been excused Blazers, but still need ties and top buttons done up. After half term they can wear house shirts, which are Polo-shirts.

I don't think you will find many private schools taking the line of "if you don't like it, take your DCs elsewhere". That attitude is most often found in oversubscribed state schools, especially superselectives.

As other posters have said you are the customer and they would be mad to ignore the concerns of parents.

My DSs prep school does allow shirt sleeve order when it is hot, which sensible. I think it is announced at assembly at the beginning of the day. However, at the end of the day they have to put blazers and ties back on to walk out the door and walk 20 across the playground to the waiting parents cars, which I think is rediculous.

Don't call it a 'relaxation' of rules.

Our school is the same as happygardening's. We are very strict on uniform and in summer follow the army rule of "shirt sleeve order"; it is not a relaxation, it is a different set of rules. They have to do jacket off, tie off and sleeves rolled above the elbow - you can't mix and match between winter and summer rules eg jacket on but tie off.

Your DD wearing a collar and tie is apeing male clothing therefore the male dress code of short sleeve order should also apply. Slay 'em with logic.