Science lessons in most Welsh schools are good but assessment isn't robust enough, according to school inspectors.
Estyn also says sometimes, in primary schools, teachers pass on their science misunderstandings to pupils.
The Welsh Government welcomes the report which it says is broadly positive.
More top news
Turning increasingly cloudy with rain affecting western parts by mid afternoon. Rain spreading eastwards but drying up overnight.
More powers for Wales, a ban on income tax rises and more free childcare are at the heart of the Conservative's Queen's Speech.
A woman who refused to get married as a 'fat bride' tells GMB she shed six stone after a nasty jibe about her weight left her in tears.