Validation of objects inside array of jsonb objects with RubyOnRails

How would you validate each object inside an array of object with Rails?

I am building a user profile form in our Rails app. Inside user model, we have basic string attributes but some jsonb fields as well. JSONb fields default to [] because we want to store an array of objects inside that attribute. Here is an example of simplified user model attributes:

• name: string
• email: string
• education: jsonb, default: []

Education is an array of objects such as:

[{
  school: 'Harvard university',
  degree: 'Computer Science',
  from_date: 'Tue, 11 Jul 2017 16:22:12 +0200`,
  to_date: 'Tue, 11 Jul 2017 16:22:12 +0200'
},{
  school: 'High school',
  degree: 'Whatever',
  from_date: 'Tue, 11 Jul 2017 16:22:12 +0200`,
  to_date: 'Tue, 11 Jul 2017 16:22:12 +0200'
}]

User should be able to click Add school button, to add more fields via jquery. That jquery part is not important for this question - maybe just an explanation why we used an Array of objects.

How would you validate each item in education array, so I can mark the text field containing validtion error with red color? I got adviced that using FormObject pattern might help here. I have also tried writing custom validator that inherits from ActiveModel::Validator class, but the main problem still lies in fact, that I am dealing with an array, not actual object..

Thanks for any constructive help.