The promise is a virus of some sort (TBD) takes out all the children and a percentage of adults in a fairly short amount of time (hours to days). Hand Waved (for now) as an immune system thing (children's are less developed, and some adults would be susceptible). The percentage of adults would be weighted a bit more towards western countries, but global nonetheless.
According to my research, that would be roughly 2.5 billion people (1.9 billion children on earth and 0.6 billion adults to get up to ~35%). Obviously anything based around childcare would fall apart, teaching would cease to be a career for 5-15 years. But how much else would fail? Would our society of specialists fall apart? Would it be safe to assume that everything would regress back to the level it was when we were last at 4.5 billion people on earth (early 70s)?
What would the effects be 1 year out? 5 years out? 10 years out? And how long would it take to recover back to today's type of society (not necessarily population level, but the same capabilities)?