Secondary school blazer sizing

[BunTooti]

Help! please.
I'm having to order DDs uniform online and although I've measured her and looked at the size chart I'm still unsure what size to order.

I want it to last but don't want it to be huge, if she measures 32" does that mean I buy the 32 or do people generally buy a 33 or 34 to allow for shirt, jumper, growing...

That's before factoring in if the uniform is even true to size .

I've never bought a suit jacket or blazer before, I feel clueless.

What age is she and what dress size?

My dd started in a 34 and moved to a 36 by the time she was 14 I think. She is a ladies size 10

Do you know anyone at the school that would let you try on their child's blazer? I did this for one of my neighbours

She's almost 12 and a size 4-6. She's exactly 32 across the chest now but could easily grow by September.
I don't know anyone who already goes.
I guess I could order a couple of sizes and return whatever doesn't fit.

She's almost 12 and a size 4-6.

My daughter is in year 7, size 6 and 5’4” and we bought a 32 inch blazer for last September when she started secondary. It still fits fine so I’d say 32” is probably the right size. It’s hard buying online though. We bought in a school shop but weren’t allowed to try anything on due to covid last summer, we ended up buying 2 sizes of everything and taking the wrong size back.

Thanks @SupermanInk that's helpful.
She's got quite small shoulders and waist so I don't want it to look like it's burying her. It really is difficult buying it all online when we have no idea what the sizes are like.
And so expensive