No, School is not necessary and I work with many guys who went to school and are angry that they wasted there time going there and are still paying back there loans. In our Business, you learn on the job. Everyone gets paid the same. It doesn't matter if you have been in the Business 1 day or 20 years, the pay is the same. I am in the union and have 1 job. In non union work, they will throw you on the camera 1 day and the next you could be doing grip or electrical or both at the same time. Its great if you know what you are doing but paying for film school is stupid when you can learn for free on the job.
Now, if you want to be a director or Director of Photography, You will need to know lighting, grip and camera depts jobs well. If you plan on making your own shows and putting them on the internet( dint waste your time trying to sell something to the studios, its like winning the lottery and everyone in the Business is already trying to do it.) then you will need to go to film school.
if you have any questions, let me know. firstname.lastname@example.org