|Bad Penny joined the class when her strip ended.|
Some people think that Leo Baxendale drew The Swots and the Blots from the very beginning in Smash!, but that's not so. The series that ran in the comic from the first issue in 1966 to the last Odhams issue in early 1969 were mainly drawn by Ron Spencer and Mike Lacey, two artists imitating Leo's style. (Nigel Parkinson reminded me that Leo did draw one episode before then. See the footnote in this post.) Leo took over the strip when Smash! was revamped by IPC in March 1969. In doing so, he completely re-energised the strip, making the characters more distinctive. It had always been an enjoyable strip but Leo made it even funnier!
Here's a handful of examples of Leo's Swots and Blots from Smash! in 1969.
Leo wrote and drew the majority of The Swots and the Blots strips in the IPC Smash! (although some were fill-ins by Les Barton and Terry Bave) and it proved popular enough to transfer to Valiant and Smash! in 1971 when the two comics merged. Even today, it's still one of the funniest strips to have appeared in a British comic!
UPDATE: As Nigel Parkinson reminded me, Leo did do one Swots and Blots before the comic was revamped. Here it is, from Smash! No.159, dated 15th Feb 1969...