I say yes, though it should be as non-denominational as possible (unless it's a denominational environment), and parents should still retain the right to opt their children out of it (whereupon the teacher just makes them just go sit quietly in the corner
... with their eyes shut so they don't see the meditation happening
It could be promoted as a cross between discipline, mental health and promoting a calm and sane school environment.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)
"To argue with a person who has renounced the use of reason is like administering medicine to the dead" - Thomas Paine