Potential Schooling Ponies?

These are my beloved ponies. They live outside all year round, and are mainly ridden by my little sister a few times a week. They are all welsh mountain ponies, and are getting older (aprox. 17 yo) and I was thinking about turning them into schooling ponies.
I need a second opinion. (Sorry about the dirt and the matted manes, I haven't gotten to pull their manes yet this year)

Fantasia
(This is my dutch warmblood, I'm just looking for a critique for her)
I used to show jump with her, but she's too old now and has bad knees.


Hulsten


Ollie (front) Taya (back)


Bibi (Sorry for the bad picture)


Taya (she has mild founder, so she can only walk and trot)

The horses are beautiful, but it's difficult to say anything useful about their conformation going off of these pictures.