Why "Big School" was a big disappointment, BBC1, Episodes 1-4 review

I expected this to be great. Look at the cast, the premise, the writers. It was puerile, predictable and dull. Got a laugh with the principal (Frances de la Tour - last seen in the dreadful "Vicious") taking home the confiscated booze. As an retired teacher I thought I'd get a few more giggles. The opening bit with the David Walliams' spectacular science experiment - would a teacher sequence a lesson like that? I know this is a comedy, but it put me off to start with. Ogling and groping Catherine Tate and talk of erections, silly old duffers going to the toilet in the wrong place .... please... thought I was watching Benny Hill.
Hope later episodes improve.
UPDATE
Have now watched episodes 2-4. Still pretty awful. Frances de la Tour came out of it unscathed - had the best lines. Talent show had its moments - David Walliams' flute business.
David Arnold opening theme music - classy, as always. Episode 3 - more broad humour and one dimensional characters. The drugs theme was tired. Perhaps if more of the characters were vaguely likable, it might help.
The intro scene with Pat, the lab assistant, was "Little Britain" territory. Catherine Tate has not a lot to do,   with lines like,"Thank you for not fingering me." Oo-er, nurse.
The Principal having a joint in her office....lame. Luke, the pretentious Music teacher, reminds me of Mr G. from "Summer Heights High"
Episode 4 - the school play/Maasai warrior script was the pits. An embarrassment, had to look away at times, it was so cringe-worthy. The tossing off/overcoat reference by Walliams/Mr Church was a new low. Why am I still watching this dross? Going by the preview of Episode 5 (more dick jokes), I'm not bothering to watch anymore. This crap has been sold to Australian commercial television. It won't rate. Imagine this dross with edited to fit into a 30 minutes block (including 9 minutes of advertisements).
Just watched "Bad Education" (Series 2, first ep). Also terrible. A shame, as I like Jack Whitehall's work. Best thing was seeing the actor who played Kylie in "Beautiful People" again.

If you want to see a funny show about high schools - Chris Lilley's "Summer Heights High".
Bring back "Please Sir!" (1970). Or even U.S. remake: "Welcome Back, Kotter"