I respectfully believe you are grossly misinformed. Do you know any teachers personally? It varies across the country, but local teachers are paid half the salary of managers and software developers after receiving the same amount of education, yet they're expected to spend every waking hour dealing with students. Here are some concrete numbers for a junior high teacher:
7 classes per term, average of 40 students per class = 280 students total. There are 7 classes per day of 45 minutes each, with 5 minutes between classes and a 30 minute lunch. Teachers have to meet with students before and/or after school and monitor students between classes, so they're typically at school and busy for 8 hours or more per day with no breaks except maybe lunch. You try locking yourself in a building with 1000 or more shouting young teenagers for 8 hours straight without so much as a bathroom break.
If a teacher assigns a homework assignment every day and spends three hours per day (at home) grading assignments, then each student gets less than one minute of attention per assignment. Every student has his or her own points of confusion on the subject matter, which cannot be addressed in just one minute per day, and using class time to broadly address the questions of a few students slows down the students who don't have the same questions.
Notice I didn't include any time for designing lesson plans and presentations, writing grant proposals, creating assignments, or meeting with parents, let alone spending time with their families (which often enough just doesn't happen).
Regarding "furniture problems:" desks are a fixed size, they have to be spaced apart enough for students and teachers to reach them without tripping, and the classroom also needs presentation space at the front, a teacher's desk, and storage space. Fire codes specify maximum occupancy limits for rooms. There's only so much room available for desks.
Maybe you have to see the combined exasperation and exhaustion of an overworked and underpaid teacher to appreciate the level of decay present in our public school systems. This is an area where averages and statistics are misleading.