When talking about the philosophy of idealism, what are some contemporary examples in art education?

While Idealism is a complex philosophical theory with various proponents and many different versions, the version that is most pertinent to the field of art education is the one espoused by Hegel. Hegel, a nineteenth-century German philosopher, published his Aesthetics in 1835, and the first English translation appeared some forty years later—thus the influence of this work went far beyond his native Germany. His philosophy is called "idealistic" because he claimed that ultimate reality was in the mind or spirit (Geisst in German)—it was, in that sense, ideal. Idealism also holds that understanding the self is a key to understanding reality. For Hegel, understanding of the self requires a synthesis between the self and the external world, and art has an important role to play in this synthesis.
In Hegelian aesthetics, the most important function of art is to expose the truth in the material form of art. Beauty arises from this reconciliation of matter and form that only art is capable of. Art—along with religion and philosophy—is one of the three ways in which we can apprehend ultimate reality, so for Hegel, art occupies a much more central position than it did for many of his contemporaries.
Hegel's impact on art education came through figures like the American educator, William Torrey Harris, who was an important figure in art education in the nineteenth century and sought to apply Hegelian principles in art education in various educational institutions. In an address to the National Education Association in 1889, Harris said:

The cultivation of taste, the acquirement of knowledge on the subject of the origin of the idea of beauty (both its historic origins and the philosophical account of its source in human nature), the practice of producing the outlines of the beautiful by the arts of drawing, painting and modeling, the criticism of works of art with a view to discover readily the causes of failure or of success in aesthetic effects.

These were ideas that were clearly influenced by Hegel. Harris, was also influenced by earlier Romantic idealists such as Amos Bronson Alcott and Elizabeth Peabody. Idealism was important for art education because it was a foil for aestheticism. Art was more than something frivolous or something additional to a regular curriculum—it was seen as an important site of self-understanding and moral and political transfiguration.
In the contemporary world, the effect of these strands of thought can be seen most clearly in the educational philosophies of Montessori and Waldorf schools, both of which take art education to be essential to a holistic curriculum.