I'm sorry for posting here, I play sax, but a soprano sax and a clarinet are close....right?
I can't play any of the high notes...(well for me) high D above the bar and up to High F# I know there must be some advice out there for hitting higher notes...

I always here our Clarinet talking about who can hit the highest notes so I was wondering if you could give me some advice

also how does one maintain tone and stay in tune in such a high register?

different enough that saxophone players would probably be a better help. really the mouthpiece-area-stuff is the biggest difference, and that's the biggest effect on high notes.

Okay well i find with the clarinet the reed quaility and hardness makes a big difference.. I use a 2.5 reed and I can hit the high notes(3rd octave) but, 2.5 is harder to blow then a 1 as you could expect.. a 1 I would struggle to get any of the high range and i have been playing for a while..also if you have an old clarinet and the pads perhaps have a tiny leak of air, it can make it a little harder again.