No. There was no art school, as we know them today during the Renaissance. Leonardo studied at Verrocchio's Workshop as an apprentice to master Verrocchio.
No. Artists didn't go to art school in the Renaissance times. They became apprentices at a master's workshop and learned the trade that way. In Leonardo da Vinci's case, he was an apprentice to...
He was an apprentice to an artist named Ghirlandaio. He also was allowed to sketch and study the private museum of Lorenzo de Medici. Addition: There were no art schools in those days.