I thought I knew the rules

[aTUfan]

It's 2nd and 10 on the opponents 15.
Incomplete pass into the end zone, but defensive interference.

Where do you place the Ball?
What down is it?

It is different for college, pro and high school in some states

 

[cmullinsTU]

College I think is half the distance to the goal, automatic first down.

NFL I believe ball is placed at the 1 and auto first down.

No idea about HS.

 

[aTUfan]

College I think is half the distance to the goal, automatic first down.

NFL I believe ball is placed at the 1 and auto first down.

No idea about HS.

Texas and Mass. hs use ncaa rules.

The game I was watching was a California HS game.

Ball placed on the 7.5. Replay 2nd down.

 

[Babe the Blue Ox]

In High School, only the “Roughing” penalties come with an automatic first down. Roughing the kicker, passer, etc.

Half the distance and replay 2nd down is correct in your example.