I think the waterloo logo is like this as it represents the school being unorganized as the letters are jumbled up. also the letters are school table showing the show is in a school.
I think that the the producers chose this different range of cast members because they have a different range of personalities this attracts a wider range of audiences for example the comedic side of the cast may attract teenagers.
Waterloo road its broadcasted at 8pm on a thursday. i think its broadcasted at this time as it represents a school day and the audience may watch as if the events had happened that day.