You were lucky! Our class from elementary school until the final day in Lyceum was always around 30. The elementary school, in the beginning housed two schools, one in the morning and one in the evening. When I was in the forth grade they brought two more schools, while they started negotiations with the owners of a near by site to built another school building. So in order to house the extra kids each class got to spend one year at some ready made class sized houses that were put in the already small play yard of the school, at the vast basement or the warehouses that were quickly cleared. It was not the best of places to contact lessons and mind you it was the early to mid 80ies, when Greece was considered blooming economically! Nobody protested and to tell you the truth we were too young to even bother. It was fun to us back then.
Then the Gymnasium and Lyceum (high school, I guess) was a building reminiscent of a huge prison, ground floors had bars and all, and housed two schools as well, morning and afternoon. It was the late 80ies and early 90ies, another blooming period for Greece! But we never saw the inside of a lab, we used to excersize during the gym class on old matresses and a couple of basket balls and to top it all the new school at a near by site was delayed so we had to use the basements and every other possible room to house the exesive number of pupils. And we were already 30 in each class!
Imagine my surprise, when I, together with some mates, while searching the surroundings of the buildings, we found a marble plaque taken down and let to rot, that stated that the building was built by the dictator George Papadopoulos during the junta in 1967-1974! It was such a let down for our democratic beliefs. And what's more as we grew up we found that most schools and roads and many public buildings were built during that period! The democratically elected governments, couldn't built a school in 10 years! And they had to give the building of roads to the private sector, which means that the roads were never meant to finish, or became to expensive (either to built or to travel on-due to the high tolls)