Some master's skis are not bad. Fischer RCs come to mind... I like them so much I have 3 pairs. They would put up with your average 23m set, but maybe not so much in 26-30m sets. They're very stable considering the twitchy 18-19m radiuses... length is ok, the 185cm is I think 19m.
The question really is "how good and how fit is your kid?" - they're not racing FIS, right? Gliding on a ski is always better than pushing it around! For HS racing, a stable 19m can smoke almost anything... For around here, going to division 2 (non-FIS) with anything bigger than 23m means you have the cojones... or that's what your dad found on sale -insert guilty smile- !
Realistically, we train a lot more than we race and at this age and level, I might put more value on training, than racing fast! So, what's your training set on average? 30m?
Just for reference, since I just remembered about it, here's a 23m ski in an ~18-19m set - it *can* be done:
p.s. We carried 2 pairs to every non-FIS race, 18m and 23m and the selection was based on conditions!