Ha, ha,ha, fuck no. Not a fucking chance. You won't get respite either.
Strategies that help?
ADHD, a fuck ton of caffeine. (Ask other people for more ideas)
School are not meeting her needs. Meet with the Sendco and try and get some accommodations in place. (Quiet space, time out, movement breaks,) They will blame you for shit parenting. This is normal. Do a parenting course. It will either help, or provide evidence for assessment.
Autism strategies:
As soon as she is out the school door, feed her something sugary, and something with complex carbs. Heavy back pack, tight hug. Rock her side to.side. do OT calming activities every day. Try sunglasses or ear defenders big hoody,
No demands, (no questions, no chat, no shopping , no changes of routine) keep her separate from the others. They go in the car while you rock and calm. Or she goes in the car to calm while you three play outside. If you walk she goes one side, held, the others go the other side. You need to be responsible for her emotional regulation until she is capable herself.
You need to keep them separate at home. Strictly supervised.
Learn her triggers. Prevent them. (Great fun if one's autism stims trigger the other's meltdowns)
If she is in meltdown she will not respond to words or discipline. She may not remember what she has done. Safe space on her own or tight hug or rocking may help. Prevention better than cure. You need to be responsible for this, though it will mostly be school who wind her right up.
Lots of decompression time. Lots.
Daily OT will help. Ask for a referral. It might be quicker.
Ask if they have pre diagnosis parent information sessions.
Try to reframe your thinking that this child is overwhelmed and scared. It helps most of the time. Yes I've typed this before, then had to bloody work hard to put into practice and probably will again.
Get sensory toys. Try the works or Amazon. Beware of price hikes for the label sensory toy.
Check uniform for labels and general discomfort.
If school are shit, move her. Find a better one.