Elementary here. They manage the school. More than just a boss for the teachers, they ensure all facets of the school run smoothly, from front office to custodial crew, to cafeteria, to classroom. A principal will also work with students who have discipline needs (although that sometimes falls to APs in unless it is egregious). They determine where and how money coming into the school will be spent and make various curriculum decisions with input from faculty. A good principal is worth their weight in gold. They really set the tone and culture on the campus.
Quick rundown of today: bus duty (supervising students entering school), lap around school greeting/chatting with each teacher, announcements, grade level meeting, emails, parent conference ( listening to invalid complaint), went and got coffee for secretaries, teacher conference, went around to classrooms on patrol for knuckleheads, phone call with asst superintendent, parent conference (more complaints), emails, check lesson plans, lunch duty (monitor cafeteria), return phone calls, meeting with transportation director, emails, take sick student home because no one answers phone at 4 diff numbers, afternoon announcements, dismissal bus duty (monitor late bus students), emails, another parent conference, leave school, take 2 phone calls from teachers on the way home...at home: answered more emails, several text messages, and 2 more phone calls from teachers
And that's just what I can remember! It's busy but I have the greatest job in the world! I have the most awesome students and staff ever. Even though the parents can be challenging, I always try to approach it from their POV and hear their concerns.
I hope this helps answer your baby's question!
Edit: got to school at 6:45 am left at 4:45 pm
"The boss of the teachers" is a pretty good description. Among other things, they make sure the rest of the faculty are doing their jobs.
They observe teachers and write evaluations. They discipline problem students. They have meetings with staff to plan curriculum, events, etc. They have meetings with parents. They have meetings with district administrators about policy changes. They oversee the budget and spending for their school. They look after the overall physical building and request repairs when needed. They meet with the PTO. They write reports for the district. They write grant proposals. They deal with security issues. And a good principal (in my opinion) will just spend some time walking around their school, keeping an eye on things and talking to their students and staff.
They're essentially managers. And the key role of any manager (again, in my opinion) is to isolate their employees from as much crap as possible that prevents them from focusing on their jobs. For a principal, that means taking care of all the administrative bullshit so that their teachers can focus on teaching.
I have a fabulous elementary school principal, and it makes all the difference in the world. In addition to what's already mentioned here, I'll just add that a good principal advocates for students and staff and helps them make connections with resources outside the school. My principal goes to administrative meetings and asks for everything from money, to extra staff, to equipment, to policies that will support our school. She also stands up for us when the district wants to do things that are not good for our students. She has the specialized knowledge about state education laws and the experience to weigh in on policies with authority. At least once she has stopped something that would have been illegal and made my job very difficult before I even knew about it. She is the person who finds a local business to subsidize musical instruments for our low-income students, and then she also makes arrangements for our students to perform at community events. Especially at a smaller school a good principal will create an environment full of cooperation and support, and I think it really makes a difference in the happiness and effectiveness of teachers and staff.
Edit: A word
Their primary function is money. There is so much of it that goes into a school, and they have to figure out where much of it goes. They also have duties in evaluating teachers.