Up until what age should young boys and young girls be allowed to play with each other on the block and in the neighborhood?
A very, very young age. As soon as the boy puts on his ציצית and his yarmulke, try to train him in his future career of להתרחק מן הנשים. Of course, right now, it doesn’t mean much to him, but keep him away. Even though they’re very young, keep them apart.
This is a very important principle. The עם ישראל is a holy nation. And the gentiles are soaking in טומאה. They always were, but today even more than before. And it’s very important that boys and girls be kept apart.
Now, once upon a time, the עם ישראל had not yet been spoiled by the gentiles and was קדוש. We find that רב יוחנן testified that he remembers in ארץ ישראל that there was a time when the boys and girls of sixteen and seventeen played together on the street. And no wrong thoughts came into their minds (:בבא בתרא צא ). When the atmosphere is perfect all around you, it’s a different world. But today it’s a world full of clouds, full of darkness. There is a thick smoke blocking out the spirituality, the רוחניות. Everyone is טמא today. Just by breathing the air in the street we absorb the טומאה.
And therefore today, it’s so important להתרחק מן הנשים, to keep away from women. The woman is a צדקת and you’re a צדיק. You’re both צדיקים. Keep away! No matter how righteous you are and no matter how righteous she is – keep away. Keep away! להתרחק מן הנשים is a very important lesson and you should start teaching that lesson as early as you can.