Gakkatsu!

Class debates over small problems, similar tone 

almost the same story both of them have this weird teacher and it shows their comedy situations with the class. 

Both Gakkatsu and Hetalia are comedy anime that last 5 minutes per episode. While Gakkatsu contains more slice-of-life elements, they share a style of humor. 

Both those shows contain: - The weirdest art styles imaginable. - A short run time per episode. - A slice of life/school setting. - Fast-paced humor. - Energetic characters (Mai/Mi and Chino especially.) that have charm at their best and are just plain retarded at their worst. - A share of WTF'ery at times. (Though in Ai Mai Mi it happens a lot more often.) If you like one, you might like the other. 

They both deal with subjects that pertain to everyday life. Both aim to make you laugh and are good at it.  

Both have similar female protagonists. Chiho Takachiho and Suzumiya Haruhi are both energetic girls and a lot of the humor (especially from Gakkatsu) comes from random events or statements.  

They are both short comedy series that are about students coming up with random stuff, just Seki-kun plays alone during class and in Gakkatsu the whole class takes part in the discussion. 

Both series contain Discussion + Humor, and short. 

Both have bizarre humor and situations as well as primitive yet somewhat creative animation and character art.