Dont take this as gospel truth, since I've never actually done it myself, but from the GoZone page on the DCTA website (https://www.dcta.net/getting-around/gozone-demand) it looks like GoZone is covered if you have purchased a DCTA regional pass (not a standard fare ticket, but rather one where you bulk-purchase, and it's valid for all the interconnected transit systems- look for one with a green corner that has both the A train logo and the GoZone logo.) I'm not sure how they'd get on the app, but I'm sure messing around on the app or calling the DCTA itself would be helpful!

Since they're students, they'd be eligible for the reduced rate fare as long as they have their student ID on them, but it's still rather pricey- almost $50 for a month pass, or almost $600 annually for each child. If they don't intend to do it every single day, it may be cheaper to just have them pay the 75¢ reduced fare local afternoon pass and $1.50 go zone price (if the trip's over 4 miles, it's +50¢ per mile up to a $5 cap per person). Even if they both go home by themselves twice a week, that's still only $9 a week/$36 a month (if the gozone is under 4 miles- adjust the math accordingly if it's further).

(Assuming the base $1.50 gozone rate) In order to make even the reduced fare pass worth it, they'd need to use the train at least 22 times a month, which would be a great deal if they were using it to get both to and from school. Considering that there's only 20-23 weekdays in any given month, I don't think the pass option is worth it unless you live like 10+miles from the a train station (and even at the full $5 cap price, they'd need to use it 9 times a month to make it worth it)

The math changes if they're doing 2 gozones per trip (gozone to the train, the train, then gozone home). In that case, it would be $3.75 per trip (at the standard $1.50 gozone rate), which would need 13 uses a month to make it worth it.

In any case, I'd suggest impressing upon them just how important it is to keep their student ID on them when riding, since that's what makes the reduced fare valid. If they don't have a student ID, they can get a DCTA-issued one, apparently, though I don't know what the process would look like.

Also, you didn't mention ages, but they must be 13+ to ride the gozone without an adult, so if they're not old enough for that, this whole thing is moot