that's interesting. The Thai Embassy in Singapore told me very recently that the Education - Gardian Visa for one year was still available. We applied for a three month tourist visa in the end as it suited our needs better. I believe it can be extended multiple times in the current COVID times in which we live. I did also double check the Education Visa with the Phuket International school who sent me details on it. Anything less than a year would be unworkable as you need to enroll children into school for the whole year.
Your children can get a visa based on them going to school, I think it's a Non Ed Visa and you get one each as their parents - 1 child can have 1 parent as a guardian. It's very cheap, £100 each or similar. But they need to enroll into school upfront I believe.