The ending of the school year depends on when you start. If you start earlier in August, then the school year ends earlier. If you start later, then the school year ends later. I started school this year on August 18th I think, and the school year ends June 4th.
Actually, the age for school is 5-any age. You can always attend a college class, but people usually don't when they are 40 or up.
That may be correct in some US states, but not all. And certainly not over on this side of the pond. Loads of Adult education here in the UK. The government spends millions/billioms each year.
As an example, in a small (very small) place like Selsey, where I live, there are many locations with many courses:
http://wsgfl.westsussex.gov.uk/ccm/navigation/school-list/all-establishments---by-type/adult-education-centres/selsey-adult-education-centre/;jsessionid=a6janQzGQW-a
And schooling can start at the age of 3. (Nursery school)