i have always been of the opinion that the highest 'legal' note of a Bb clarinet is a high 'C' (thumb and register key)
this is because;
1) the fingerings become erratic
2) theres usually more than 3 fingerings for each note, and
3) unless you are good at them, they just sound like controlled squeeks
this is not to say that you shouldnt play higher than the 'c', i use them regularly

i was just wondering what other peoples opinions are on this matter. please let me know

Play as high as you're able-- the wonderful thing about these instruments is there isn't a defined top of the range

However, for playing in songs, I don't think going above the high G (the one above the C you mentioned) is plausible, because the entire section would need to be able to play it.