Is not writing a zero in the ones place when writing a decimal number a new thing in math?

Like this .5 or .898 instead of 0.5 and 0.898

I was taught you have to have a zero, and that's how I teach my kids, and that's what my textbook uses when writing numbers.

But every year I get kids from other schools who swear they were told they didn't have to put a zero. In the past, these kids haven't exactly been top students, so I kind of discounted their protests but just said, "Well, now you do. The zero helps you notice the decimal point as something other than a period or a stray mark. It helps you remember that this is a number that is less than zero."

This year, though, I have a student who is very bright and "with it" and she swears she was taught that the zero is optional.

Am I behind the times? If so, what's the rationale for no leading zero?

I don't mark it wrong. I encourage them to use the 0 so it helps them recognize the decimal point as more than a stray mark as you said, but I don't mark it wrong.

.5 and 0.5 are the same thing. Both have 0 in the ones and 5 tenths.

When setting up decimals like these in multiplication problems, I actually tell my sped kids to not,write them because it clutters up their problems so much. They get the answers right when they don't include the zeros.

I teach high school science. I train them to use the zero, because it is a convention scientists use. I don't mark it wrong if they do not...I just encourage the habit. It seems to be something they haven't been expected/required to do before ninth grade, but they don't find it confusing. So I would say it's a good habit, but not a requirement.

I'm in Canada. I was taught that you use the zero when using the metric system.
My mom, who was a nurse, would say that you need to use it when medication is prescribed. There would be a dangerous chance of an overdose. The zero makes it very clear that there is a decimal amount.

i teach 6th, and i point out to my students that they will usually see the zero on worksheets and other problems that i haven't made. i explain its purpose and then tell them that i don't waste my own time writing it but to decide on their own.

(i had never heard anyone say that you SHOULD use the zero---until this thread.)

When I teach 3rd grade I teach the zero and make the students use it. When I teach 4th, I use the zero for demonstration. I don't make them use it unless the student is having problems with keeping the place values lined up. By 4th grade the students should have enough number sense to know the purpose of the zero and why it isn't necessary.
Just they way I do it. You should do what works for your students.

I was taught it was optional as well. I explain the purpose and give them the choice to use it or not. My sped students get confused with too many digits in a problem.

I'm old as the hills, but I was never taught to use a leading zero. In 4th I teach it with the leading zero, because that's what my students were taught. But other than that, I don't.