The School District is charging Defendants $25 per unexcused absence for Failure to Attend School. I have not found anything saying they can or cannot do this.
Anyone have advice?

Absent express statutory authority, I would hesitate to continue this practice. Generally, fees must be authorized, and even absent any "prohibition" unless there is specific authority, then the fee is not proper.

I don't think that this type of restitution would be allowed under Article 42.037, CCP, and I think that this sort of practice is what is getting Senator Whitmire and the Legislature heavily involved in how truancy is handled next session. Creative thought, though!

The Comptroller has a habit, especially when funds are scarce, of reviewing the books of local courts, trying to find fees they deem to be "unauthorized." If it does find such a fee, the Comptroller informs the County that the it cannot keep the money, under an unjust enrichment theory, and a full refund must be made. The Comptroller then tells the County that it is impractical to track down each individual defendant, and personally refund the fee. So the Comptroller orders the County to pay the money directly to the State.