By the color of their robes, they seem to be Burmese kids. Burmese monks do meditate a lot. I read somewhere that monks in Pa-Auk Monastery are advised to meditate around 17 hours a day.
But even if they were not Burmese, what is wrong about it?
SN 35.127 wrote: "How can it come about, Bhaaradvaaja, depending on what is it that these young monks, youthful, black-haired, with the bloom of youth, in the prime of life, never having enjoyed the pleasure of the senses, can practice the holy life fully and perfectly to the end of their days?"
Two seven-year-old Arahats were Samanera Sumana and Samanera Pandita (Sukha) (Ref: Dhammapada V. 382 & V.80)
Thag 6.10 wrote:When I was seven
& newly gone forth,
having conquered with my power
the great powerful serpent,
I was fetching water for my preceptor
from the great lake, Anotatta,[1]
when the Teacher saw me & said:
"Look, Sariputta, at that one,
the young boy coming there,
carrying a pot of water,
well-centered within,
his practices — inspiring;
his bearing — admirable.
He's Anuruddha's novice,
mature in his powers,
made thoroughbred by a thoroughbred,
good by one who is good,
tamed by Anuruddha,
trained by one whose task
is done.
He, having reached the highest peace
& realized the unshakable,
Sumana the novice
wants this:
'Don't let anyone know me.'"