['My son had always done so well in school.', 'That is good, is he struggling now?', 'Yes, lately he has been slacking off it seems and he failed a test.']
Did you ask him about it, or did he make a big change to high school. Sometimes a big change or just burn out can kick in.
My son had been doing really well in school. Lately he has been slacking off and not turning stuff in.