Lizzie is quite familiar with the routine.
The three year-old toddler knows that time for bed is not time for tears.
Her mother, Laura Downes, a special needs primary school teacher from London soon made bedtime rules clear.
She says: "It needs to be rigid and the same and, actually for us, that meant we had a sort of fail-safe tool to fall back on. So, whatever had happened in the day or whatever kind of what was going on, we knew the routine was coming up; she knew the routine was coming up."
According to a research published online in the Journal of Epidemiology and Community Health, regular bedtimes can help children to perform better at school.
The study of more than 10- thousand youngsters revealed their cognitive development is affected by inconsistent bedtimes.
Three, five and seven year-old children were associated with lower scores in reading, mathematics and spatial awareness.
The results were very similar both on boys or girls.
Professor Amanda Sacker, report contributor and member of the Department of Epidemiology and Public Health at the University College, in London, says sleeping is important:"You just need sleep to consolidate all that you've learnt and experienced from the day before, so that this gets, sort of, laid down in your brain as memories and so on; so you just need to have sleep for that. And also, people's body rhythms might be affected by inconsistent schedules."
Emma Janes, is a sleep practitioner.
She also agrees on the importance of regular bedtimes and she says that some children need to be taught how to sleep: "We learn to sleep. So everyone assumes we just know but for some children they need teaching it. And we know that children thrive on routine. They love to know 'what, when, where, why, how'. By changing that routine, we are going to impact on their sleep."
The research authors also point out that irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation.
Scientists believe the lack of sleeping routines can also undermine the plasticity of the brain and the ability to acquire and retain information.
So, for children like Elizabeth Downes, "early to bed" will surely make her "healthy, wealthy and wise."