"Crazy" vandals attacked two schools leaving a trail of destruction which could cost more than £10,000 to repair.
The attackers smashed windows and lights at the Bradford schools - including one only recently opened.
The damage at Feversham Girls' College and Swain House First School, Radcliffe Avenue, was the latest in a string of attacks at both complexes.
The vandals smashed more than 70 windows at Feversham College - currently in temporary accommodation while waiting to move into an £8 million purpose-built school - and broke into the school's science block.
The toll of vandalism has risen to more than 200 windows broken this year alone.
In Swain House, on the same site as Feversham College, more than 40 windows were smashed and security lighting outside the school was attacked.
Councillor David Ward (Lib Dem, Idle) who holds the portfolio for education called the vandalism "crazy and mindless". "We have been taking measures across the district to prevent vandalism which seems to have worked but it is very unfortunate that it has not worked in this particular case.
"In some schools at particular risk we have had 24-hour cover.
"This is crazy, stupid behaviour which costs us thousands, money that could be better spent on books and teachers. Security costs a phenomenal amount now."
Swain House's new head teacher, Dianne Rowbotham, who is due to begin her job next week, was horrified by the attack.
She only returned home from a holiday in Portugal on Sunday to be confronted with the damage yesterday. She said: "I take up the new post in September, so this is not a good start.
"I went to see the damage with the relief caretaker Alf Hamilton and the police. Vandals have smashed light fittings and windows but have not attempted to break in, so at least there is no internal damage."
One part of the school was brand new this year and has only been used by pupils for a few months.
Workmen have been carrying out internal refurbishment to some of the offices in the new building. Keys were only handed over on Friday.
Miss Rowbotham, who was previously deputy head at Girlington Primary School, added: "Windows will be boarded up and then repaired this week."
Keyholder Mr Hamilton estimated that both schools would have a repair bill of at least £5,000.
"It is very costly for the schools but this is what they have to do in this day and age," he said. "The cost of the damage will run into thousands."
Schools in the Bradford district are regular targets for vandals.
Just before the summer holidays, parents of pupils St Augustine's CE Primary School on Wapping Road complained of many attacks, including 50 smashed windows, costing thousands of pounds.
In June, Undercliffe Primary School suffered graffiti and broken windows and arsonists caused more than £50,000 of damage at Heaton Primary School in January last year.
St Oswald's CE primary school in Great Horton had its newly refurbished building smashed up in March last year, also costing several thousand pounds.
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