I agree it is not a route I would recommend, but it is a route that is used. It avoids Balkerne Hill and North Hill which are both steep hills, plus it cuts off at least ten minutes walk to the station. Teenagers being teenagers....
If you know it's there then you know to forbid your child to use it.
It's actually pretty safe during the day, lots of families cycle and walk there and a lot of the issues took place in a neighbouring residential area (and in Hilly fIelds, Enfield in London). But I wouldn't want Dd walking home there by herself, just as I wouldn't want her walking in any semi-deserted open space at dusk.
I know that there will be several forum members who will be sending their DC 45-50 miles each day to school in Colchester, but I'm curious as to how something happening in Enfield makes it undesirable to walk from Colchester North station to Lexden Road at eight o'clock in the morning?