grammaticality - Can You Use "It Is Because" to Explain Your Opinion

For background I work in ESL as an assistant, and I give a native's perspective, but sometimes I doubt myself.

My students have a habit of writing "it is because" to explain why they think something (or, rather, they use it for everything). For example:

"I agree that school uniforms are good. It is because they are easy to wear."

They try to use "it" to refer to why they think this way. To me, this seems off. I checked around and found that most of the time when referring to something for the first time "this" or "that" are normally used, and that they are also used for ideas. I also feel that when you're talking about something personal, like your opinions, you don't use "it."

Would I be able to correct this to "this" and have it make sense grammatically? The other teachers (non-natives) think that "it is because" is fine in this context, but it still feels off to me. I generally try to keep my corrections close to their original work so that they can more easily understand what was wrong which is why I want to know if I should correct this to "this is because." Or, does "it is because" work in this context?