To buy 100 pencils the school needs 100 * $1.80 = $<<100*1.80=180.00>>180.00.
Each ice pop sells for $1.50 but costs $.90 to make, for a net profit of $1.50 - $.90 = $<<1.50-.90=.60>>.60.
So in order to raise $180.00, the school will need to sell $180.00 / $.60 per ice-pop = <<180/.60=300>>300 ice-pops.
#### 300